Auger Spectra and Different Ionic Charges Following 3s, 3p and 3d Sub-Shells Photoionizatio

乙酰丙酸成氢键的红外证明
乙酰丙酸是一种常用的有机化合物，其分子式为C5H8O3，结构中包含了一个羧基和一个甲酰基。

在乙酰丙酸分子中，羧基上的氧原子能够和氢原子形成氢键，这是一种特殊的分子间相互作用力。

通过红外光谱分析，可以确定乙酰丙酸中氢键的存在。

红外光谱是一种常用的分析技术，其原理是利用物质分子中的化学键振动和拉伸，吸收特定的红外光谱线。

每种化合物都有特定的红外光谱图谱，通过分析样品的红外光谱图，可以确定化合物的结构和成分。

在乙酰丙酸的红外光谱图中，可以通过特定的吸收峰来确定氢键的存在。

羧基上的C=O伸缩振动会在1740-1760 cm-1范围内产生一个比较强烈的吸收峰，这是由羧基上的C=O键振动引起的。

而在氢键的存在下，C=O伸缩振动的波数会发生变化，通常会出现一个红外光谱峰的移位或者分裂。

此外，羧基的C-O伸缩振动也会受到氢键的影响。

正常情况下，C-O的伸缩振动会在1200-1300 cm-1范围内产生吸收峰，但在氢键的
存在下，这个吸收峰也会出现变化。

因此，通过分析乙酰丙酸的红外光谱图谱，可以确定其分子中存在氢键的证据。

在实际的红外光谱分析中，通过与标准样品的对比或者使用红外光谱数据库，可以更加准确地确定乙酰丙酸中氢键的存在。

因此，红外光谱分析是一种非常有效的方法，可以用来研究乙酰丙酸分子结构中的氢键。

总的来说，通过红外光谱分析可以证明乙酰丙酸分子中氢键的存在。

红外光谱图谱中的特定吸收峰和波数变化，都可以作为乙酰丙酸中氢键的红外证明。

这种分析方法为化学研究和分析提供了有力的工具，有助于深入理解有机化合物的结构特性。

惠森，朱旭浩，刘小玲，等. 牡蛎源肽锌纳米粒体外胃肠道消化稳定性及作用机制[J]. 食品工业科技，2023，44（11）：38−44. doi:10.13386/j.issn1002-0306.2022110206HUI Sen, ZHU Xuhao, LIU Xiaoling, et al. Stability and Mechanism of Oyster Peptide Hydrolysate Zinc Nanoparticles during in Vitro Gastrointestinal Digestion[J]. Science and Technology of Food Industry, 2023, 44(11): 38−44. (in Chinese with English abstract). doi:10.13386/j.issn1002-0306.2022110206· 青年编委专栏—食品营养素包埋与递送（客座主编：黄强、蔡杰、陈帅） ·牡蛎源肽锌纳米粒体外胃肠道消化稳定性及作用机制惠　森1，朱旭浩1，刘小玲1，张自然2,*（1.广西大学轻工与食品工程学院，广西南宁 530000；2.北部湾大学食品工程学院，广西钦州 535011）摘　要：本研究旨在探究体外模拟消化对牡蛎源肽锌纳米粒（OPH-Zn ）稳定性及其结构的影响，揭示OPH-Zn 在胃肠道消化过程中的动态变化规律。

采用各种光谱仪（紫外、红外和荧光）、电镜（扫描和透射）以及粒度仪测定模拟消化液中OPH-Zn 的锌含量、表面形貌、二级结构以及粒径分布变化。

研究发现，OPH-Zn 总锌含量高达228.89±2.53 mg/g ；在模拟胃液消化过程中，OPH-Zn 和ZnSO 4对照中可溶性锌含量变化不大，且两个样品无显著差异（P >0.05）；转为模拟肠液消化时，OPH-Zn 和ZnSO 4的锌溶解性分别降低了28.07%和55.31%（P <0.05），与ZnSO 4相比，OPH-Zn 可溶性锌含量显著高于ZnSO 4（P <0.05）；光谱分析发现，OPH-Zn 在模拟胃液和肠液中保持相对稳定，但在由胃液过渡到肠液时，Zn 2+与肽键中氧原子和氮原子的配位作用发生变化，电镜结果显示不同消化程度的OPH-Zn 表面微观结构和颗粒大小也存在一定差异。

LIBS光谱技术用于分析钾盐矿成分刘浩森;杨再荣;麻仲恺【期刊名称】《化工技术与开发》【年(卷),期】2022(51)3【摘要】我国的钾盐供需紧张,长期依赖进口,因此,钾盐矿中钾元素的快速准确分析,对确定矿场的开采价值有着重要的意义。

本文建立了基于激光诱导击穿光谱(Laser induced breakdown spectroscopy,LIBS)技术结合偏最小二乘(Partial least squares,PLS)的方法,用于钾盐矿成分的快速分析。

采用LIBS光谱仪收集了30个钾盐样品的光谱,首先基于钾盐矿LIBS原始光谱构建了初始PLS模型,探究了3种光谱预处理方法(一阶导数、小波变换、归一化)对该模型预测性能的影响,重点研究了小波变换(Wavelet transform-Partial least squares,WT)中不同的小波基函数以及分解层数对模型性能的影响。

为了降低其他元素的光谱数据对模型预测性能的干扰,构建了基于钾元素特征波段(404.41nm、766.48nm和769.89nm)的PLS校正模型。

采用五折交叉验证法,对PLS模型、LIBS光谱的预处理方法及特征波段等进行优化。

基于优化后的输入变量及模型参数,建立了钾盐矿的LIBS偏最小二乘模型。

相比基于原始光谱的偏最小二乘模型,该模型的R2 p从原始光谱的0.7856提升到0.9575,RMSEp从0.2176降低到0.1546,MRE从0.2530降低到0.1632。

研究结果表明,基于LIBS技术结合偏最小二乘法,是一种可用于钾盐矿成分快速准确分析的方法,可为钾盐矿开采过程中钾元素的定量分析提供一种新思路和新方法。

【总页数】5页(P73-76)【关键词】LIBS光谱;钾盐;小波变化;偏最小二乘【作者】刘浩森;杨再荣;麻仲恺【作者单位】西安石油大学化学化工学院;中国石油天然气股份有限公司大港石化分公司【正文语种】中文【中图分类】O657.38【相关文献】1.近红外光谱技术结合主成分分析法用于子宫内膜癌的诊断2.美国对水产品的技术性贸易壁垒/抗病毒亲虾繁养的大规格南美白对虾卖高价/日本从大马哈鱼中提取胶原/诊断鱼病的DNA试纸/日本研究枪乌贼活体远程运输技术/大豆粉经高温灭活胰朊酶后蛋白吸收效果好/日规范有机农产品的表示方法/韩规模化人工培育红海参苗种/日本从扇贝壳中提取钙结晶抑制物/能快速分析饲料成分的红外光谱仪/不同品种的杂交技术可用于珍稀鱼类繁育3.基于远程LIBS-Raman光谱的火星矿物成分分析方法研究4.基于LIBS光谱与成分分析的飞机蒙皮激光除漆可控性研究5.双脉冲LIBS技术成功用于钢水成分在线分析因版权原因，仅展示原文概要，查看原文内容请购买。

利用二维光子晶体提高波的耦合效率(英文)
欧阳征标;安鹤男;阮双琛;李景镇;张道中
【期刊名称】《光子学报》
【年(卷),期】2004(33)1
【摘要】通过多重散射方法数值模拟研究和实验测量表明利用二维光子晶体可以提高波的耦合效率研究发现 ,高的波耦合效率通常发生在光子禁带的边沿和其它非禁带区的某些频率处当光子晶体的晶格常数接近于所传输的波的波长时 ,会出现很高耦合效率的共振耦合现象利用二维光子晶体的情况下的波耦合效率最高可以达到不利用二维光子晶体时的 1.89倍
【总页数】4页(P69-72)
【关键词】光子晶体;耦合效率;共振耦合;光子禁带;光集成器件;晶格常数;传输性能【作者】欧阳征标;安鹤男;阮双琛;李景镇;张道中
【作者单位】深圳大学工程技术学院固态光子实验室;中国科学院物理研究所光物理开放实验室
【正文语种】中文
【中图分类】TN491;O734
【相关文献】
1.二维光子晶体耦合器耦合特性分析 [J], 关春颖;苑立波
2.高品质因子和高传输效率的二维光子晶体耦合腔波导研究 [J], 吕冬妮;沈宏君;余建立
3.一种0.3 THz二维光子晶体定向耦合器的设计 [J], 陈琦;何晓阳;张健
4.一种0.3THz二维光子晶体定向耦合器的设计 [J], 陈琦;何晓阳;张健;
5.利用干涉光刻和双光子聚合技术制造带有功能缺陷的二维光子晶体(英文) [J], 孙慧婷;宋正勋;翁占坤;王大鹏;蒋伊爽;于烨
因版权原因，仅展示原文概要，查看原文内容请购买。

一种高信噪比铷原子频标物理系统祁峰;赵峰;王芳;夏白桦;梅刚华【期刊名称】《计量学报》【年(卷),期】2011(032)001【摘要】物理系统是铷原子频标的核心部件,通过分析物理系统原子鉴频信号信噪比对频标频率稳定度的影响机理,对物理系统内部结构进行了改进.改进后的物理系统采用了优化的开槽管微波腔,用Xe气作为起辉气体的铷光谱灯,采用分离滤光的三泡设计方案.对改进后的系统进行了初步测试,秒稳定度约为8×10(-13).此结果表明铷原子频标的稳定度可以突破1×10(-12)/τ(1/2),铷原子频标的长期稳定度还有进一步提高的潜力.【总页数】5页(P80-84)【作者】祁峰;赵峰;王芳;夏白桦;梅刚华【作者单位】中国科学院武汉物理与数学研究所原子频标实验室,湖北,武汉,430071;中国科学院研究生院,北京,100080;中国科学院武汉物理与数学研究所原子频标实验室,湖北,武汉,430071;中国科学院武汉物理与数学研究所原子频标实验室,湖北,武汉,430071;中国科学院武汉物理与数学研究所原子频标实验室,湖北,武汉,430071;通信指挥学院,湖北,武汉,430012;中国科学院武汉物理与数学研究所原子频标实验室,湖北,武汉,430071【正文语种】中文【中图分类】TB939【相关文献】1.基于开槽管腔的高信噪比铷原子钟物理系统 [J], 许风;郝强;王鹏飞;明刚;梅刚华2.铷原子频标物理系统小型化设计 [J], 康松柏;赵峰;王芳;祁峰;夏白桦;梅刚华3.一种铷原子频标频率综合器新方案的设计与实现 [J], 黄争;阎世栋;梅刚华;钟达4.一种小型铷原子频标功率稳幅电路 [J], 罗奇;包婉静;秦蕾;高伟;余钫5.一种用于微小型铷原子频标的6.83 GHz谐振腔 [J], 魏秀燕;吴静;夏瑞;郭航;;;;因版权原因，仅展示原文概要，查看原文内容请购买。

316L不锈钢抗氢脆性能研究白彬,张鹏程,邹觉生(中国工程物理研究院,四川绵阳621900)摘　要:用光学显微镜、电子显微镜、俄歇电子谱/二次离子质谱表面分析仪等结合拉伸试验,研究了316L奥氏体不锈钢及其电子束焊缝在650℃充氘后组织、微区成分变化与性能的关系,以及拉伸应力与氘分布的关系。

结果表明,高温气相充氘后,316L奥氏体不锈钢及其电子束焊缝抗氢脆性能明显下降。

晶界、孪晶界析出大量碳化物,但拉伸断口形貌并未呈沿晶断裂;晶界上未发现S、P等痕量元素的偏聚,却产生了富Cr、M o的贫Ni层,这表明晶界成分的变化减弱了晶界析出物对氢脆的影响。

电子束焊缝塑性下降,拉伸时从该处断裂。

拉伸静水应力梯度分布导致氘在拉伸试样断口处富集。

关键词:奥氏体不锈钢;氢脆;焊缝中图分类号:TG142.71 文献标识码:A 文章编号:100023738(2002)0520018203H ydrogen Embrittlement R esistance of316L Austenitic Stainless SteelBAI Bin,ZHANG Peng2chen,ZOU Jue2sheng(China Academy of Engineering Physics,Mianyang621900,China)Abstract:The effects of the microstructure change and grain boundary composition change in316L austenitic stainless steel on its resistance to hydrogen embrittlement are investigated by optical microscopy,SE M,AES and SI MS.The deuterium dis2 tribution dependence of tension stress is als o studied.The hydrogen embrittlement susceptibility of316L stainless steel and its elec2 tron beam welding seam with charged D2at650°C is increased.The tensile fracture surface shows both ductile dimples and sec2 ondary cracks,although an am ount of carbide precipitates along the grain and twin boundaries.Meanwhile,no segregation of trace elements S,P and C occurs at grain boundary,but a Ni2depleted and Cr,M o2rich layer is formed.This indicates that the grain boundary composition change impairs interaction of the precipitates on carbide2matrix interface with hydrogen,and then this im2 proves the resistance to hydrogen embrittlement.The plasticity of electron beam welding charged at650°C is decreased,and the tension samples rupture from welding seam.M oreover,the deuterium richens in fractures of the tension samples because of static stress.K ey w ords:316L austenitic stainless steel;hydrogen embrittlement;electron beam welding seam1　引　言Fe2Cr2Ni系奥氏体不锈钢的奥氏体组织稳定性显著影响其抗氢脆性能。

Graphene/Substrate Charge Transfer Characterized by Inverse Photoelectron SpectroscopyLingmei Kong,†Cameron Bjelkevig,‡,§Sneha Gaddam,‡Mi Zhou,‡Young Hee Lee,|Gang Hee Han,|Hae Kyung Jeong,⊥Ning Wu,†Zhengzheng Zhang,†Jie Xiao,†P.A.Dowben,†and Jeffry A.Kelber*,‡Department of Physics and Astronomy,Nebraska Center for Nanostructures and Materials,Theodore Jorgensen Hall,855North 16th Street,Uni V ersity of Nebraska s Lincoln,Lincoln,Nebraska 68588-0111,United States,Department of Chemistry and Center for Electronic Materials Processing and Integration.Uni V ersity of North Texas,1155Union Circle #305070,Denton,Texas 76203-5017,United States,Department of Physics,Department of Energy Science,and Center for Nanotubes and Nanostructured Composites,Sungkyunkwan Ad V anced Institute of Nanotechnology,Sungkyunkwan Uni V ersity,Suwon,440-746Korea (ROK),and Department of Physics,Daegu Uni V ersity,Gyeongsan,712-714Korea (ROK)Recei V ed:September 9,2010;Re V ised Manuscript Recei V ed:October 26,2010Wave vector-resolved inverse photoelectron spectroscopy (IPES)measurements demonstrate that there is a large variation of interfacial charge transfer for graphene grown by chemical vapor deposition (CVD)on a range of dielectric or metallic substrates.Monolayer graphene grown by CVD on monolayer BN(0001)/Ru(0001)exhibits strong charge transfer from the substrate to graphene of 0.07(1)e -per carbon atom,as manifested by filling of the π*band and displacement of the Fermi level.IPES measurements of CVD single layer graphene on Ru indicate a substrate-to-graphene charge transfer from the substrate of 0.06(1)e -per carbon atom,in agreement with reported angle-resolved photoemission results.The IPES spectra of CVD single layer graphene on Ni(poly)and on Cu(poly)indicate 0.03(1)e -per carbon atom charge transfer from Ni and Cu substrates.Single layer graphene has also been grown by free radical-assisted CVD on MgO(111),resulting in a layer of graphene and an oxidized carbon interfacial layer between the graphene and the substrate.IPES measurements indicate that 0.02(1)e -per carbon atom charge is transferred from graphene to the MgO substrate.Additionally,IPES and photoemission data indicate that single layer graphene/MgO(111)exhibits a band gap.These data demonstrate that IPES is an effective method for precise measurement of substrate/graphene charge transfer and related electronic interactions,in part because of the extreme surface sensitivity of the technique,and suggest new strategies for extrinsic doping of graphene for controlled mobilities for device applications.1.IntroductionGraphene,due to extremely high room temperature electron/hole mobilities 1-3and polarizabilities,4,5is of great interest for nanoelectronic and spintronic device applications.Interfacial interactions of graphene with adjacent layers are therefore of practical importance,as both adsorbate-induced charge transfer and interaction with dielectric substrates can result in signifi-cantly enhanced or reduced mobilities.Of interest for device applications,adsorbate-induced hole or charge transfer generally results in reduced mobilities but has resulted in enhanced Hall mobility,6while proximity to high-k dielectric substrates sometimes yields increased electron or hole mobility at room temperature,apparently through screening of carriers from charged impurities.7Graphene/substrate interactions may also yield a band gap in the graphene band structure,8and this is of critical concern in the development of graphene-based logic devices with true “off”states.Recently,wave (k )-vector resolved inverse photoelectron spectroscopy (IPES)has demonstrated the presence of substan-tial BN-to-graphene charge transfer 9for graphene grown byCVD on BN(0001)/Ru(0001).An order-of-magnitude enhance-ment of graphene room temperature mobility relative to graphene/SiO 2has recently been reported 10for graphene sheets physically transferred to BN substrates,consistent with predicted results for extrinsic doping,6but also possibly due to decreased phonon interactions with hexagonal BN(0001)layers.These facts,combined with monolayer sensitivity,11demonstrate the potential for IPES to delineate electronic interactions between graphene and substrates in a layer-by-layer fashion and to provide a quantitative basis for predicting the effects of such materials interactions on graphene electronic properties.We report here the results of IPES measurements of electronic charge transfer between graphene and various substrates,including BN/Ru(0001),Ru(0001),Ni(poly),Cu(poly),and MgO(111),as well as previously reported 12IPES data of graphene on SiC(0001).Notably,the IPES and photoemission data indicate the presence of a band gap for graphene/MgO(111),suggesting that graphene on this substrate may be of particular utility for logic device applications,with the band gap allowing a true “off”state.IPES data further indicate that significant interfacial charge transfer and band-filling do not appreciably alter the fundamental conduction band electronic structure of graphene and suggest practical routes toward the formation of extrinsically doped graphene layers with controlled electron mobilities for device applications.*To whom correspondence should be addressed.E-mail:Kelber@.†University of Nebraska s Lincoln.‡University of North Texas.§Present address:Intel Corp.,4100Sara Rd.SE,Rio Rancho,NM 87124.|Sungkyunkwan University.⊥Daegu University.J.Phys.Chem.C 2010,114,21618–216242161810.1021/jp108616h 2010American Chemical SocietyPublished on Web 11/17/20102.Experimental MethodsThe fabrication of the monolayer graphene/BN/Ru(0001)sample,and characterization by scanning tunneling microscopy/spectroscopy (STM/STS),low energy electron diffraction (LEED),Raman spectroscopy,photoemission spectroscopy (PES),and IPES measurements,has been previously reported.9The data are included here for direct comparison with results for graphene on other substrates.Graphene on Ru(0001)was prepared in a manner similar to that described in the literature 13by CVD of C 2H 4at 1×10-8Torr,2min of exposure at 700K on Ru(0001),followed by annealing in ultrahigh vacuum (UHV)to 1000K,in a UHV system described previously.14Graphene layers on polycrystalline substrates s Ni(poly)and Cu(poly)s were prepared by CVD and characterized as described previously.15,16A graphene film was also grown by CVD using thermally dissociated C 2H 4(free radical assisted CVD;FRA-CVD)on a MgO(111)single crystal substrate in a system equipped for LEED and X-ray excited photoelectron spectroscopy (XPS),which has been described previously.17,18A more detailed account of the preparation and characterization of graphene films on this surface,and the associated interfacial chemistry,will be published elsewhere.Briefly,a MgO(111)substrate 1cm in diameter and 0.5mm thick was cleaned at room temperature by exposure to atomic oxygen from a commercially available thermal catalytic cracker (Oxford Applied Instruments).A flux of dissociated C 2H 4was supplied from the same source,which has also been described previously.19,20XPS spectra were acquired at a constant pass energy (44eV)using Mg K R radiation and analyzed using commercial software (ESCA-TOOLS)according to standard methods.IPES data were acquired as described previously,21,22in the isochromat mode using a Geiger -Mu ¨ller detector set to detectphotons at 9.7eV.The IPES measurements were limited by aninstrumental resolution of ∼400meV.The IPES spectra were acquired along the surface normal.Thus,the relative positions of the π*and σ*bands in the IPES data reported here are at the Γpoint of the Brilloin zone,at the σ*minimum.9,12The angle-integrated PES and wave vector-resolved IPES were undertaken to study the molecular orbital placement of both occupied and unoccupied orbitals of graphene on MgO but here have not been corrected for final state effects arising from the insulating nature of the substrate,which may lead to an overestimation of the true band gap.In addition to such effects,the angle-integrated nature of the PES measurements and wave vector-resolved nature of the IPES measurements obviate the use of these data to determine energy splitting between specific valence and conduction band features,such as the π-π*splitting.PES data were acquired using a He I source UV source (21.2eV)in the same vacuum system and with the analyzer aligned with the surface normal.3.Results3.1.Characterization of Single Layer Graphene on Ru(0001).A cleaned and ordered Ru(0001)single crystal was exposed to 1.2L of C 2H 4at 700K,followed by annealing to 1000K in UHV.A sharp,bifurcated LEED pattern was observed (Figure 1a),due to the Ru and graphene lattice mismatch.Assuming a Ru lattice constant of 2.7Å,the outer diffraction spots (Figure 1b)indicate a lattice constant of 2.5(1)Ås graphene.The thickness of the graphene overlayer was estimated from decreases in intensity of a Ru Auger feature (Figure 1c,arrow),which does not overlap with the C(KVV)Auger ing a calculated 23inelastic mean free path of 10.5Å,a total average thickness of the graphene layer afterFigure 1.Characterization of single layer graphene on Ru(0001).(a)LEED (beam energy )70eV)after 1.2L C 2H 4exposure to Ru(0001)at 700K,followed by annealing to 1000K in UHV.(b)Line scan of LEED pattern,showing bifurcated spots.(c)Auger spectra before/after ethylene exposure and annealing.Changes in peak-to-peak height for marked Auger feature (arrow)were used to calculate changes in intensity and therefore average thickness of carbon overlayer.Graphene/Substrate Charge Transfer Characterized by IPES J.Phys.Chem.C,Vol.114,No.49,201021619annealing is estimated at 1.3((0.2)monolayers.The uncertainty in this figure derives from the fact that the experimental error in the reproducibility of absolute Auger electron intensities in this system,conservatively estimated at 10%.Exposure of this sample to ambient resulted in no discernible evidence of oxidation as determined by Auger or changes to the LEED pattern.3.2.Characterization of Single Layer Graphene on MgO(111).A graphene film was grown on an MgO(111)single crystal by first cleaning the surface in atomic O at room temperature and then exposure of the (disordered)MgO surface to a flux of dissociated C 2H 4at ∼600K (5×10-7Torr,25min).No LEED pattern was observed before or after the exposure to dissociated ethylene.From the C(1s)XPS spectrum (Figure 2a),a total average carbon thickness of 3Åwas determined.The sample was re-exposed to ambient and placed on a different sample holder to permit more efficient heating.Subsequent annealing to 1000K in UHV produced the observed change in C(1s)XPS (Figure 2a).(Because of the significant and variable sample charging,the peak maxima of the two carbon spectra have been aligned to compare changes in peak shape.)The total average thickness of the carbon layer after annealing to 1000K was 2.5Å,indicating that exposure to ambient and subsequent annealing in UHV had resulted in no significant increase in surface carbon.The annealing process did,however,result in a significant broadening of the C(1s)spectrum (Figure 2a)toward higher binding energy,indicating the presence of surface carbon in multiple oxidation states.After annealing,the expected 6-fold LEED image for a graphene film was observed (Figure 2b).Because atomically clean MgO(111)(1×1)yields a 3-fold LEED pattern at this beam energy (∼75eV),24the presence of a 6-fold LEED pattern indicates formation of a graphene surface layer.This conclusion is corroborated by the fact that decomposition of the XPS spectrum of the annealed sample into two regions s one centered near 292eV binding energy (uncorrected for charging)with the same fwhm as the spectrum prior to annealing and the second including the higher binding energy tail s indicates that the thickness of the lower binding energy component is 1.5Å,corresponding to a monolayer of graphene.The XPS data in Figure 2,however,indicate that carbon is present on the MgO surface in multiple oxidation states.Subsequent exposure of the annealed sample to ambient resulted in no significant changes to the LEED pattern (Figure 2b).The LEED and XPS data together therefore indicate the formation of an ordered graphene layer in thepresence of an interfacial layer that includes carbon in higher oxidation states.3.3.Inverse Photoemission Measurements of Interfacial Charge Transfer.The position of a specific conduction band feature in the IPES spectrum,relative to the Fermi level,provides quantitative information on charge transfer between substrate and graphene layers.The IPES data are displayed in Figure 3for single layer graphene on BN(0001)/Ru(0001)(Figure 3a),on Ru(0001)(Figure 3b),on Cu(poly)(Figure 3c),on Ni(poly)(Figure 3d),and compared to the previously reported 12data for multilayer graphene grown on SiC(0001)by thermal evaporation (Figure 3e)and to our results for graphene/MgO(111)(Figure 3f).Although charge transfer between the single layer graphene and the SiC substrate is known to dependFigure 2.Graphene formation on MgO(111)(a)C(1s)XPS spectra after exposure of a clean,disordered MgO surface to dissociated ethylene at 5×10-7Torr,25min at ∼600K (open circles),and after subsequent exposure to ambient and annealing in UHV to 1000K (solid line).The two spectra have been manually aligned and have not been corrected for sample charging.(b)Corresponding LEED pattern at 75eV beam energy after annealing to 1000K.Figure 3.IPES spectra of graphene on various substrates as labeled (background subtracted):(a)BN(0001)/Ru(0001),(b)Ru(0001),(c)Cu foil,(d)Ni foil,(e)SiC (adapted from ref 12),and (f)MgO(111).Features are labeled as (1)scattering from the π*,(2)σ*and low lying π*,and (3)σ*(Γ1+).21620J.Phys.Chem.C,Vol.114,No.49,2010Kong etal.on the Si(n type)vs C(p type)nature of the substrate surface termination,25,26such interface effects(including band gap formation)are rapidly screened upon multilayer graphene formation.8Because the data of Forbeaux et al.(Figure3e)were acquired for multilayer graphene,12we take the corresponding IPES spectrum as a standard for a graphene layer with a weakly interacting substrate,with negligible interfacial charge transfer. The spectra in Figure3are plotted as a function of energy from the Fermi level,E-E F.The data show the main features in the vicinity of the Fermi level and are plotted relative to the features identified for multilayer graphene on SiC,12seen also with single crystal graphite.27Because of imperfections in some of the graphene overlayers,the spectral features are similar but not identical due to scattering contributions.In addition,the features observed in IPES shift progressively closer to the Fermi level as the substrate is varied from MgO(Figure3f)to SiC (Figure3e),to Ni(Figure3d)or Cu(Figure3c),to Ru(Figure 3b),and then to BN/Ru(Figure3a).This is evidence of band-filling.28,29The IPES spectrum displays only the unoc-cupied density of states,but because the IPES spectra are extremely surface sensitive,the degree of charge transfer between the substrate to or from graphene can be quantitatively estimated from the binding energy positions of known features (e.g.,the mainσ*feature)in the spectrum relative to the Fermi level.At a charge neutral condition,the Fermi energy of free-standing graphene coincides with the conical point(the Dirac point),and the density of states is dominated near the Fermi level by the Dirac cone.26The introduction of extra electrons to graphenefills any empty states near the Fermi level E F,with states closest to the Fermi levelfilledfirst,thus decreasing the energy difference of conduction band features relative to E F.In contrast,the subtraction of electrons from graphene increases this energy difference.It can be seen in Figure3that corre-sponding features in the IPES spectra of graphene on Ni,Cu, Ru,and BN shift progressively closer to the Fermi level, indicating increasing charge transfer from the substrates to graphene.The bands of graphene on MgO,however,shift away from the Fermi level and indicate charge transfer from graphene to the MgO substrate.The amount of charge transfer can be calculated from the shift of the Fermi level relative to the conduction band edge.A larger shift indicates more charge transfer.The amount of charge transferred is proportional to the shift of the Fermi level for small amounts of charge transfer, because of the density of states being dominated by the unique band structure near the Fermi level.The amount of charge transfer roughly equals the shift of the Fermi level×0.02e-/ carbon atom.1For larger shifts,a density of states correction is required.Quantitative measurements of interfacial charge transfer derived from the IPES spectra(Figure3)are listed in Table1.Results of the analyses of the IPES spectra in Figure3are in agreement with results obtained by other experimental methods or by theory.The IPES-deduced charge transfer from BN(0001)/ Ru(0001)to graphene(Figure1a)indicates a substrate-to-graphene charge transfer of-0.07(1)e-/carbon atom(the negative sign indicating substrate-to-graphene charge transfer and the number in parentheses indicating the uncertainty in the last digit),in qualitative agreement with DFT calculations and consistent with a pronounced red shift of the2D Raman feature for this system(Table1).9This value is less than the previously reported value9due to the assumption(Figure3and Table1) of a charge neutral condition for multilayer graphene on SiC, not assumed previously.The interlayer charge transfer results obtained from analysis of the IPES spectra of single layer graphene/Ru(0001)(Figure1b),-0.06(1)e-/carbon atom,are in good agreement with the result of-0.05e-/carbon atom obtained by angle-resolved PES.13,30The large charge transfers determined for graphene/BN/Ru(0001)and for graphene/ Ru(0001)would indicate complete or partialfilling of the grapheneπ*band,eliminating or obscuring these features in the IPES spectrum.Consistent with this,theπ*feature is not observed for graphene/BN/Ru(Figure3a)9and is at least significantly obscured for single layer graphene/Ru(0001) (Figure3b).The result of-0.03(1)e-/carbon atom for graphene on Ni(poly)(Figure1c)is in agreement with photoemission studies indicating weak substrate-to-graphene charge transfer due to Ni(3d)/graphene(π)mixing31and in good agreement with DFT results32indicating a0.35eV downward shift of graphene band features for this reason.A similar substrate-to-graphene charge transfer is observed for graphene/Cu(poly)(Figure1d). Using the multilayer graphene/SiC IPES spectrum(Figure3e) as the“standard”for zero interfacial charge transfer,a slight [+0.02(1)]e-/carbon atom charge transfer is observed from graphene to the MgO(111)substrate(Figure3f).These latter measurements cannot be taken as accurate as thefinal state effects have not been completely excluded and cannot be taken fully into account from this data.Suchfinal state effects will result in the occupied states and unoccupied states appearing to be placed farther from the Fermi level than may be in fact true in the charge neutral ground state.33The effects of the MgO substrate on the electronic structure of graphene deposited by FRA-CVD can be determined in further detail by combining angle integrated PES and wave vector-resolved IPES spectra(Figure4).The data are plotted relative to a common Fermi level(E F).The assignment of theTABLE1:Comparison of2D Peak Positions and Substrate/Graphene Charge Transfersample a G peak position(cm-1)2D peak position(cm-1)IPES-determined chargetransfer(e-per carbon atom)b remarks/charge transferSLG/BN(0001)/Ru(0001)1540924009-0.07(1)previously reported value,-0.129 SLG/Ru(0001)no spectrum43no spectrum43-0.06(1)ARXPS value,-0.0513,30DLG/Ru(0001)159943267843042SLG/Cu(poly)159044267844-0.03(1)SLG/Ni(poly)158045,46270945,46-0.03(1)-0.02SLG/SiC1591.547271047-0.0227MLG/SiC15904827204808SLG/MgO+0.02(1)a SLG,single layer graphene;DLG,double layer graphene;and MLG,multilayer graphene.b A negative charge transfer number refers to charge donation from the substrate to graphene(n type doping);a positive charge transfer number refers to charge transfer from graphene to the substrate(p type).The amount of charge transfer equals the shift of the Fermi level×0.02e-/carbon atom.The number in parentheses is the uncertainty in thefinal digit.Graphene/Substrate Charge Transfer Characterized by IPES J.Phys.Chem.C,Vol.114,No.49,201021621valence band features in the PES spectrum is in good agreement with results on,for example,Ni(111),34while the conduction band features are in accord with assignments for graphene/SiC(0001).12The inversion of relative π/σand π*/σ*ordering (Figure 4)reflects the angle-integrated nature of the PES spectrum as opposed to the k -resolved nature of the IPES measurements.Significant sample charging was encountered for graphene/MgO(111),and in this case,the placement of the Fermi level is approximated from the position of a copper contact to the sample.The resulting placement of the Fermi level near the top of the valence band edge (Figure 4),however,is consistent with observed (Figure 3f)slightly p type doping of graphene by MgO.A band gap is observed for graphene/MgO(111)(Figure 4).The magnitude of the band gap,∼1eV,is independent of the precise placement of the Fermi level.The presence of a substantial band gap is consistent with charging encountered for the monolayer sensitive-IPES and LEED measurements.A previous brief report 35also suggested the formation of an insulating or semiconducting graphene film resulting from carbon evaporation onto MgO(111).4.DiscussionThe above data demonstrate the utility of IPES for assessing interfacial charge transfer between graphene and dielectric or metallic substrates.These data also suggest new device ap-plications for certain graphene/dielectric heterostructures.The results for graphene/BN/Ru indicate substantial charge transfer to graphene,essentially filling the π*band.9Adsorbate-induced charge transfer has been correlated 6with order-of-magnitude increases in electron mobility.Recent transport measurements on graphene sheets physically transferred to BN substrates 10indicate just such a factor of 10increase in room temperature mobility relative to graphene/SiO 2.Other factors,such as substrate phonon effects,may have impacted the above result.However,the correlation between observed charge transfer in graphene/BN heterojunctions 9and predicted 6and observed 10effects upon electron transport are certainly motivation for further study of such systems for device applications.This is the first report of the structural (LEED),chemical (XPS),and electronic (PES,IPES)characterization of graphene layer formation on MgO(111).The results,showing the presence of a band gap,are consistent with a brief abstract published previously for graphene deposition by MBE on this surface 35but indicate that the formation of a graphene layer (Figure 2)is associated with the formation of an oxidized carbon interfaciallayer.Indeed,the higher binding energy tail of the XPS C(1s)spectrum obtained after annealing to 1000K (Figure 2a)is similar to the XPS C(1s)spectrum for graphene oxide.36Band gaps varying from ∼0.237to 1.7eV 38for oxidized graphene flakes have been reported.However,the XPS data (Figure 2a)indicate two layers of carbon,while the surface sensitive LEED (Figure 2b)and PES/IPES measurements (Figure 4)indicate a graphenelike surface layer,with intact πand π*features.One possibility is that the sample consists of an oxidized carbon interfacial layer,hexagonally ordered,interacting with a graphene overlayer.The similar hexagonal symmetry of both layers would lead to A -B symmetry breaking in the graphene layer,and similar arguments have been advanced for formation of a 0.26eV band gap for single layer graphene on SiC(0001).3The evolution of the oxidized carbon region upon annealing (Figure 2a)further suggests that this oxidized carbon interfacial layer reflects a fundamental aspect of carbon/MgO(111)surface chemistry at elevated temperatures.The possible formation of BN(0001)and then graphene/BN heterojunctions on MgO(111)are suggested by these data,as a route toward the formation of extrinsically doped graphene layers on a high-k dielectric films and for moderating the effects of carbon/MgO interfacial interactions for device applications.The fact that MgO(111)can be grown on Si(100)39is further motivation for examining this system from the point of view of future device applications.Finally,the recent report of graphitic nanoflake formation on MgO powders under CVD conditions 40suggests that graphene growth on other MgO orientations or on amorphous substrates might be possible.The effects of charge transfer on the change of the energies of graphene Raman spectral features 41-48is of practical interest in monitoring doping interactions involving graphene layers.The reported energy of Raman “G”(ring breathing mode)and “2D”(a two phonon mode)features for graphene on various substrates are therefore compared in Table 1.As shown in Table 1,the 2D position for graphene/BN(0001)/Ru is red-shifted by ∼300cm -1from the 2D energy for graphene on other substrates,and this also corresponds to a large charge transfer to graphene of 0.07(1)e -/carbon atom.The energy of the corresponding G feature s 1540cm -1s is only slightly red-shifted relative to the other G mode energies (Table 1)or to the corresponding energy in HOPG.9The other graphene Raman spectra exhibit 2D features in the region of 2670-2710cm -1,and G feature energies in the range of 1580-1600cm -1,corresponding to negligible interlayer charge transfer ((0.02e -/carbon atom).Importantly,although the monolayer graphene/Ru(0001)system exhibits significant substrate-to-graphene charge transfer [-0.0.6(1)e -/carbon atom;Figure 3],no Raman spectrum is observed for single layer graphene on Ru(0001).43This is consistent with a large charge transfer,as the strong interactions required for large charge transfers on metal substrates can also lead to overdamping of the vibrational mode intensities of graphene in the Raman spectra.The data in Table 1therefore indicate that the energies of graphene Raman features for graphene on different substrates are at best very qualitative guides to interlayer charge transfer.Our own measure of the Raman shifts,however,indicates that there is a likely mode stiffening of the G band with charge abstraction from the graphene layer,even if slight,as indicated in Figure 5.This is in consistent with the previous report for phonon stiffening in carbon nanotubes.49As a final point,it is worth noting key differences between IPES and near-edge X-ray absorption fine structure spectroscopy (NEXAFS),which is also an important probe of conduction bandFigure bined PES and IPES of graphene on MgO substrates (background subtracted).For assignment of the features in the valence and conduction bands,see refs 34and 12,respectively.21622J.Phys.Chem.C,Vol.114,No.49,2010Kong etal.structure.The IPES data (Figures 3and 4)exhibit a π*-σ*splitting of ∼2eV,in agreement with previously reported data for graphene/SiC(0001).12In contrast,the corresponding splitting in NEXAFS for graphene is ∼8eV,50with a similar value for graphene oxide.51While some effects are undoubtedly due to initial state/final state matrix element effects [the initial state in NEXAFS is the C(1s)level)]as well as NEXAFS final state excitonic interactions (hole in 1s,electron in π*or σ*),the principle difference is due to the fact that NEXAFS is an angle-integrated measurement and samples the whole of the Brillouin zone,whereas the corresponding IPES value will vary signifi-cantly with the specific geometry of the measurement because of the specific wave vector sampling.125.ConclusionIn summary,the data presented here demonstrate that IPES is a quantitative guide to the transfer of charge between graphene and metallic or dielectric substrates.The IPES data show significant charge transfer of -0.07(1)e -/carbon atom from BN(0001)/Ru(0001)9and -0.06(1)e -/carbon atom for single layer graphene/Ru(0001),more than the IPES-determined charge transfer from monolayer Cu or Ni to graphene (Figure 3and Table 1)and in excellent agreement with reported results for graphene/Ru(0001)based on angle-resolved photoemission.13,30PES/IPES data demonstrate that a ∼1eV band gap occurs for graphene on MgO(111).Furthermore,IPES data for graphene on a variety of substrates indicate that interlayer charge transfer can occur by band filling without significant distortion of the graphene electronic structure.This suggests that IPES can serve as a guide to potential graphene doping strategies based on measurements of charge transfer and effective masses calculated from dispersion measurements.Acknowledgment.Work at UNT was supported by the Global Research Consortium of the Semiconductor Research Consortium under Task ID 1770.001.Y.H.L.is supported by the Star-faculty program and WCU (World Class University)program through the KRF funded by the MEST (R31-2008-000-10029-0),and H.K.J.is supported by the Basic Science Program through the National Research Foundation of Korea funded by the MEST (2010-0004592).References and Notes(1)Novoselov,K.S.;Geim, A.K.;Morozov,S.V.;Jian, D.;Katsnelson,M.I.;Grigorieva,I.V.;Dubonos,V.;Firsov,A.A.Nature 2005,438,197.(2)Berger,C.;Song,Z.;Li,T.;Li,Z.;Ogbazghi,A.Y.;Feng,R.;Dai,Z.;Marchenkov,A.N.;Conrad,E.H.;First,P.N.;de Heer,W.A.J.Phys.Chem.B 2004,108,19912.(3)Berger,C.;Spong,Z.;Li,X.;Wu,X.;Brown,N.;Naud,C.;Mayou,D.;Li,T.;Hass,J.;Marchenkov,A.N.;Conrad,E.H.;First,P.N.;de Heer,W.A.Science 2006,312,1191.(4)Son,Y.-W.;Cohen,M.L.;Louie,S.G.Nature 2006,444,347.(5)Haugen,H.;Huertas-Hernando,D.;Brataas,A.Phys.Re V .B 2008,77,115406.(6)Hwang,E.H.;Adam,S.;Sarma,D.S.Phys.Re V .B 2007,76,195421.(7)Shishir,R.S.;Ferry,D.K.J.Phys.:Condens.Matter 2009,21,23220.(8)Zhou,S.Y.;Gweon,G.-H.;Federov,A.V.;First,P.N.;de Heer,W.A.;Lee,D.-H.;Guinea,F.;Castro Neto,A.H.;Lanzara,A.Nature Mater.2007,6,770.(9)Bjelkevig,C.;Zhou,M.;Xiao,J.;Dowben,P.A.;Wang,Lu;Mei,W.-N.;Kelber,J.A.J.Phys.:Condens.Matter 2010,22,302002.(10)Dean,C.R.;Young,A.F.;Meric,I.;Lee,C.;Wang,L.;Sorgenfrei,S.;Watanabe,K.;Taniguchi,T.;Kim,P.;Shepard,K.L.;Hone,J.Nature Nanotechnol.2010,5,722.(11)Jeong,H.K.;Komesu,T.;Yakovkin,I.N.;Dowben,P.A.Surf.Sci.2001,494,L773.(12)Forbeaux,I.;Themlin,J.-M.;Debever,J.-M.Phys.Re V .B 1998,58,16396.(13)Brugger,T.;Gu ¨nther,S.;Wang,B.;Dil,J.H.;Bocquest,M.-L.;Osterwalder,J.;Wintterlin,J.;Greber,T.Phys.Re V .B 2009,79,045407.(14)Addepalli,S.G.;Ekstrom,B.;Magtoto,N.P.;Lin,J.-S.;Kelber,J.A.Surf.Sci.1999,442,385.(15)Chae,S.J.;Gu ¨nes ¸,F.;Kim,K.K.;Kim,E.S.;Han,G.H.;Kim,S.M.;Shin,H.J.;Yoon,S.M.;Choi,J.Y.;Park,M.H.;Yang,C.W.;Pribat,D.;Lee,Y.H.Ad V .Mater.2009,21,2328.(16)Gu ¨nes ¸,F.;Han,G.H.;Kim,K.K.;Kim,E.S.;Chae,S.J.;Park,M.H.;Jeong,H.K.;Lim,S.C.;Lee,Y.H.Nano 2009,4,89.(17)Wilks,J.;Magtoto,N.P.;Kelber,J.A.;Arunachalam,V.Appl.Surf.Sci.2007,253,6176.(18)Vamala,C.;Manandhar,S.;Kelber,J.Surf.Sci.2009,603,33.(19)Manandhar,S.;Copp,B.;Vamala,C.;Kelber,J.Mater.Res.Soc.Symp.Proc.20081074,1074–I03-04.(20)Chaudhari,M.;Du,J.;Behera,S.;Manandhar,S.;Gaddam,S.;Kelber,J.Appl.Phys.Lett.2009,94,204102.(21)Choi,J.;Borca,C.N.;Dowben,P.A.;Bune,P.;Pebley,M.;Adenwalla,S.;Ducharme,S.;Robertson,L.;Fridkin,V.M.;Palto,S.P.;Petukhova,N.;pYudin,S.G.Phys.Re V .B 2000,61,5760.(22)Zhang,J.;McIlroy,D.N.;Dowben,P.A.;Zeng,H.;Vidali,G.;Heskett,D.;Onellion,M.J.Phys.:Condens.Matter 1995,7,7185.(23)Powell,C.J.;Jablonski,A.NIST Electron Effective Attneuation Lengths Database,2003,V1.1().(24)Lazarov,V.K.;Plass,R.;Poon,H.-C.;Saldin,D.K.;Weinert,M.;Chambers,S.A.;Gajdardziska-Josifovska,M.Phys.Re V .B 2005,71,115434.(25)Zhang,Y.;Tang,T.T.;Cirit,C.;Hao,Z.;Martin,M.C.;Zettl,A.;Crommie,M.F.;Shen,R.Y.;Wang,F.Nature 2009,459,820.(26)Varchon,F.;Feng,R.;Hass,J.;Li,Z.;Nguyen,B.N.;Naud,C.;Mallet,P.;Veuillen,J.-Y.;Berger,C.;Conrad,E.H.;Magaud,L.Phys.Re V .Lett.2007,99,126805.(27)Claessen,R.;Carstensen,H.;Skibowski,M.Phys.Re V .B 1988,38,12582.(28)Ding,H.;Park,K.;Gao,Y.J.Electron Spectrosc.Relat.Phenom.2009,174,45.(29)Xu,B.;Caruso,A.N.;Dowben,P.A.Appl.Phys.Lett.2002,80,4342.(30)Sutter,P.;Hybertesen,M.S.;Sadowski,J.T.;Sutter,E.Nano Lett.2009,9,2654.(31)Weser,M.;Rehder,Y.;Horn,K.;Sicot,M.;Fonin,M.;Preobra-jenski,A.B.;Voloshina,E.N.;Goering,E.;Dedkov,Y.S.Appl.Phys.Lett.2010,96,012504.(32)Bertoni,G.;Calmels,L.;Altibelli,A.;Serin,V.Phys.Re V .B 2004,71,075402.(33)Ortega,J.E.;Himpsel,F.J.;Li,D.;Dowben,P.A.Solid State Commun.1994,91,807.(34)Dedkov,Y.S.;Fonin,M.;Rudiger,U.;Laubschat,C.Phys.Re V .Lett.2008,100,107602.(35)Mohapatra, C.;Eckstein,J./link/BAPS.2009.MAR.W26.12.(36)Jeong,H.K.;Noh,H.-J.;Kim,J.-Y.;Jin,M.-H.;Park,C.Y.;Lee,Y.H.Europhys.Lett.2008,82,67004.(37)Pandey,D.;Reifenberger,R.;Piner,R.Surf.Sci.2008,602,1607.(38)Jin,M.;Jeong,H.K.;Yu,J.W.;Bae,D.J.;Kang,B.R.;Lee,Y.H.J.Phys.D:Appl.Phys.2009,42,135109.(39)Chen,X.Y.;Wong,K.H.;Mak,C.L.;Yin,X.B.;Wang,M.;Liu,J.M.;Liu,Z.G.J.Appl.Phys.2002,91,5728.Figure 5.G-band distribution of graphene on different substrates.Graphene/Substrate Charge Transfer Characterized by IPES J.Phys.Chem.C,Vol.114,No.49,201021623。