Cu-Se复合物半导体薄膜的成分分析.ppt

Contents背景实验部分结果讨论小结CuInSe2材料吸收系数105/cm调整本身的化学组分抗干扰、抗辐射匹配较好CuInSe2 CuInSe第-III-VI族元素化合物半导体，为直接带隙半导体，禁带宽度1.04eV。CuInSe2薄膜太阳能电池结构CuInSe2薄膜电池薄膜电池Cu-Se binary system重要的材料光伏太阳能电池肖特基二极管CIS的制备中间产物前体u溶剂热法u光化学u化学气相沉积（CVD）u电沉积广泛应用于无机半导体的沉积。薄膜生长：简单、成本低、条件温和、自身可控的生长率和薄膜成分。Cu-Se合成方法合成方法In this report,we describe a new electroanalytical route using combined EQCM and stripping voltammetry for the compositional analysis of Cu-Se thin films electrodeposited at different potentials.实验部分实验部分copper sulfate(99%)Selenium dioxide(99.8%)sodium sulfate(99%)sulfuric acid(98%)All chemicalsinstrumenFor voltammetry,EG&G Princeton Applied Resea-rch(PAR)263A:Model M250/270 electrochemist-ry softwareFor EQCM,Seiko EG&G Model QCA917:oscillator module(QCA917-11),9M Hz AT-cut gold-coated qu-artz crystal,Pt counter ele ctrode,Ag/AgCl/3M NaCl reference electrodeFor flow-EQCM experiments,an EG&G Princeton Applied Research Model 273A system was used and frequency changes were displayed on a Kipp and Zonen Model BD111 single pen chart recorder.A Gilson Minipuls 3 peristaltic pump was used to deliver solution to the flowEQCM system and a Valco Model 6-way slider valve equipped with 0.15 mm i.d.tubing was employed to switch and inject solutions at a nominal flow rate of 0.28 mL/min.The flow rate and a cell volume(about 0.5 mL)were enough for the deposition of thin films considering the concentration of Cu2+and Se4+ions.结果讨论结果讨论Figure 1.Linear sweep voltammograms(solid line)and the corresponding EQCM frequency changes(dashed line)for the stripping of(a)Se in 0.1 M Na2SO4 solution.Scan rate:10 mV/s.(b)Cu2Se in 0.1 M Na2SO4 solution.Scan rate:10 mV/s.To differentiate the peak due to Se reduction from that arising from Cu2Se reduction,Cu-Se film was electrodeposited at 0.1 V using 0.1 M H2SO4 containing 10 mM SeO2 and 5 mM CuSO4.After the free Se was removed from the film by applying 0.7 V for 100 s in 0.1 M Na2SO4 blank electrolyte.Electrodeposition of Cu2Se was confirmed by the cathodic photocurrent of the film upon light illumination,which is consistent with p-type semiconductor behavior.In order to further assign the peak at 0.98 V in Figure 1b,the number of electrons(n)transferred during the reduction was calculated from the slope of charge-frequency plot:Q=(nFk/M)f (1)In Eq.(1),Q is charge,F is Faraday constant,k is sensitivity factor,M is molar mass and f is frequency changes.The n value obtained from the slope was found to be 1.9,which clearly shows that the peak is due to reduction of Cu2Se:Cu2Se+2e=2Cu+Se2 (2)(c)Cu in 0.1 M Na2SO4 solution.Scan rate:10 mV/s.a pre-electrodeposited Cu film was anodically stripped in 0.1 M Na2SO4 blank electrolyte(Figure 1(c).The Cu film was electrodeposited at 0.1 V for 60 s using 0.1 M H2SO4 containing 5 mM CuSO4.Figure 2.Linear sweep voltammograms(solid line)and the corresponding EQCM frequency changes(dashed line)for the cathodic stripping of Cu-Se thin films in 0.1 M Na2SO4 solution.Thin films were electrodeposited at(a)0.1 V and(b)0.3 V for 4 kHz using 0.1 M H2SO4 containing 10 mM SeO2 and 5 mM CuSO4.Scan rate:10 mV/s.Now,the composition of electrodeposited Cu-Se thin films(free Cu,free Se and Cu2Se)was determined using combined stripping voltammetry and flow-EQCM.Figure 3.EQCM frequency(mass)changes during the electrodeposition and stripping steps.Electrolytes for electrdeposition and stripping were same as in Figure 2.Figure 4.Compositional variation of Cu-Se films electrodeposited at different potentials and determined by the procedure described in Figure 3.The error bars denote one standard deviation.Then the total Cu(free Cu+Cu in Cu2Se)was determined via anodic stripping at+0.8 V and free Cu content was calculated from the difference between total Cu and Cu in Cu2Se.Figure 5.(a)Linear sweep voltammograms and(b)the corresponding EQCM frequency changes for Cu-Se films in 0.1 M Na2SO4.Cu-Se films were electrodeposited at 0.1 V for 16 kHz using 0.1 M H2SO4 containing 10 mM SeO2 and 5 mM CuSO4.Scan rate:10 mV/s.During the first 1 kHz(less than 10nm thick),the film almost consists of free Se and free Cu.However,the amount of Cu2Se increased as the film thickness increases from 1 kHz to 6 kHz or deposition time increases as seen in Figure 5.This behavior reveals that post-chemical reaction between two elements results in the formation of Cu2Se binary compoundSummaryIn summary,a novel method which is species selective for the compositional analysis of electrodeposited Cu-Se semiconductor films was developed using combined voltammetry and flow-EQCM.The amounts of free Se and Se in Cu2Se were obtained from the frequency changes at constant potentials of 0.8 V and 1.3 V,respectively.Potential steps to 0.8 V and 1.3 V were employed to reduce free Se to Se2 and Cu2Se to Cu+Se2,respectively.Resultant total Cu was anodically stripped at+0.8 V and the free Cu content was calculated using the difference in frequency changes observed during the stripping of total Cu and Se in Cu2Se.The results showed that the amounts of free Se,free Cu and the targeted Cu2Se varied with deposition potential as well as film thickness.