CdSe纳米晶薄膜的制备与特性研究

采用真空热蒸发技术,在光学玻璃基片上生长出排列整齐、高质量的CdSe纳米晶薄膜.通过X射线衍射(XRD)、X射线光电子能谱分析(XPS)、扫描电镜(SEM)、傅里叶红外光谱(IR)等进行表征.结果表明,薄膜结晶性能较好,纳米晶颗粒约为40 ～70 nm,呈半月状,排列整齐;化学元素配比为49.4∶50.6,稍微富Se;红外透过率高,禁带宽度为1.89 eV,高于块状的CdSe晶体(1.70 eV).     

基于Si衬底的CdSe薄膜蒸镀工艺研究

采用真空蒸发技术在Si(100)基底上制备了CdSe纳米晶薄膜,利用X射线衍射仪(XRD)、膜厚测试仪、原子力显微镜(AFM)方法对不同蒸发电流下制备的薄膜的结晶情况、表面形貌进行分析表征.结果表明:蒸发电流对CdSe薄膜的结晶性能和表面形貌有显著影响.当蒸发电流为75 A时,CdSe薄膜沿(002)方向的衍射峰相对较强,沿c轴取向择优生长优势明显,薄膜厚度约为160 nm,晶粒尺寸约为40 nm,颗粒均匀;薄膜表面平整光滑,表面粗糙表面粗糙度(5.63 nm)相对较低,薄膜结晶质量较好.     

薄膜厚度对ZnO:Y薄膜结构及光电特性影响

室温下采用射频磁控溅射法在玻璃衬底上制备出了具有良好附着性、低电阻率和高透过率的新型ZnO∶Y(ZnO掺杂Y2O3,简称ZnO∶Y)透明导电薄膜。研究了薄膜厚度对ZnO∶Y薄膜结构、光电特性的影响。结果表明:不同厚度的ZnO∶Y薄膜均为多晶薄膜,具有ZnO六角纤锌矿结构,最佳取向为(002)方向。随薄膜厚度增加,其电阻率减小,当薄膜厚度增至800 nm时,其电阻率为8.36×10-4Ω.cm,迁移率为15.3 cm2.V-1.s-1,载流子浓度为4.88×1020cm-3。不同厚度的薄膜在可见光范围内平均透过率均为90%以上,当薄膜厚度从200 nm增加到800 nm时,薄膜禁带宽度从3.68 eV减小到3.61 eV。     

原子层沉积与磁控溅射法制备TiO2薄膜性能对比研究

分别采用原子层沉积(ALD)和磁控溅射法(MS)在Si和石英衬底上制备TiO2薄膜,并进行退火处理.利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、原子力显微镜(AFM)和紫外分光光度计对这两种方法制备薄膜的晶型结构、表面形貌和光学特性进行分析对比.结果显示,对于沉积态TiO2薄膜,ALD-TiO2和MS-TiO2未能检测到TiO2衍射峰.ALD-TiO2为颗粒膜,其表面粗糙,颗粒尺寸大;MS-TiO2薄膜表面平整.经退火后,两种方法制备的TiO2薄膜能检测到锐钛矿A(101)衍射峰,但结晶质量不高.受薄膜表面形貌和晶型结构等因素影响,退火前后ALD-TiO2透过率与MS-TiO2透过率变化不一致.对于沉积态和退火态薄膜的禁带宽度,ALD-TiO2分别为3.8eV和3.7 eV,吸收边带发生红移,MS-TiO2分别为3.74 eV和3.84 eV,吸收边带发生蓝移.     

Al-H共掺杂ZnO薄膜的形貌及光致发光性能研究

在不同衬底温度条件下采用RF磁控溅射法在石英玻璃上沉积Al-H共掺杂ZnO薄膜.对所有样品进行晶体结构、表面形貌、电学、光学以及室温光致发光性能分析.结果表明:随着衬底温度的升高,ZnO薄膜的结晶度增加,晶粒增大,薄膜致密度增加;薄膜表面起伏变化减小;同时,电阻率最低达到7.58×10-4Ω·cm,透过率保持在75;左右.所有ZnO薄膜样品都以本征发光为主,Al-H共掺杂在一定程度降低ZnO薄膜缺陷发光的强度;随着衬底温度的升高,ZnO薄膜的本征发光强度明显增大;同时在能量为3.45 eV附近观察到了一个紫外发光峰.     

单晶硅外延生长晶化硅薄膜的研究

采用P型单晶硅片为衬底,并经混合酸溶液腐蚀抛光、清洗后,利用射频磁控溅射镀膜系统在其表面制备非晶硅薄膜;再结合快速光热退火工艺,于N2气氛下480℃退火30 min,得到晶化硅薄膜;利用光学金相显微镜、XRD衍射仪和拉曼散射光谱(Raman)仪对单晶硅衬底和晶化硅薄膜进行结构和性能表征.研究了混合酸溶液对单晶硅表面腐蚀效果、籽晶诱导外延生长晶化硅薄膜的物相结构和薄膜带隙.结果表明:采用混合酸溶液腐蚀后得到表面平整、光滑的单晶硅衬底;非晶硅薄膜经过快速退火后受籽晶诱导生成晶化硅薄膜,其晶相沿单晶硅衬底取向择优生长;随着非晶硅薄膜厚度从80 nm增加到280 nm,晶化后硅薄膜的表面粗糙度逐渐减小,晶化率从90.0;逐渐降低到37.0;;晶粒尺寸从6.65 nm逐渐减小到1.71 nm;带隙从1.18 eV逐渐升高到1.52 eV.     

薄膜厚度对 Mn-W 共掺杂 ZnO 透明导电薄膜性能的影响

利用直流磁控溅射法在低温玻璃衬底上制备了高导电透明的 Mn-W 共掺杂 ZnO(ZMWO)薄膜,并研究了厚度对薄膜结构、光学及电学性能的影响.X 射线衍射结果表明 ZMWO 均为六方纤锌矿结构的多晶薄膜,具有垂直于衬底方向的 c 轴择优取向.薄膜厚度对 ZMWO 薄膜的晶化程度、电阻率和方块电阻有很大影响.当薄膜厚度从97 nm 增大到456 nm 时,ZMWO 薄膜的晶化程度提高,而电阻率和方块电阻减小.当厚度为 456 nm 时,所制备ZMWO 薄膜的电阻率达到最小,其值仅为8.8×10-5 Ω·cm,方块电阻为1.9 Ω/□.所有薄膜样品在可见光区的平均透过率都较高,其值约为89;.当薄膜厚度从97 nm 增大到 456 nm时,光学带隙从3.41 eV增大到3.52 eV.     

蒸发电流对CdSe薄膜的结晶性能影响研究

采用真空热蒸发技术,选取系列蒸发电流在光学玻璃基底上制备出CdSe薄膜.利用X射线衍射仪、扫描电子显微镜和原子力显微镜对样品的结构和表面形貌进行了表征.结果显示:蒸发电流为75 A时,CdSe薄膜沿(002)方向择优生长,衍射峰较强,半峰宽较小,晶粒(约48 nm)分布较均匀,表面粗糙度低(5.58 nm),无裂纹.蒸发电流不改变薄膜的结晶取向,但电流过低时,薄膜的表面颗粒轮廓模糊且有间隙,结晶性差;电流高于75 A时,随电流升高,薄膜结晶性逐步降低,颗粒变小,半峰宽变大,部分样品表面晶粒生长不完整,表面出现裂纹.     

二元掺杂对SnO2薄膜的结构与光学性能的影响

采用超声雾化热解法在石英玻璃基底上制备了SnO2/Sb:Ni薄膜,并对薄膜的晶体结构、表面形貌和光学性能进行了表征.结果表明:薄膜晶粒生长致密,晶粒大小均匀,呈柱状晶结构,(200)晶面是优势生长面.经过二元掺杂后,薄膜的平均可见光透过率最高为87.54;;波长为300 nm时,薄膜的紫外透过率约为50;.     

磁控溅射PbSe薄膜厚度对其结构及光学特性的影响

本文利用射频磁控溅射法在200℃的玻璃衬底上沉积了纳米晶PbSe薄膜,薄膜厚度分别为200 nm、250 nm、500 nm及600 nm.利用X射线衍射仪(XRD)、原子力显微镜(AFM)及紫外-可见分光光度计,分别研究了不同厚度PbSe薄膜的晶体结构、表面形貌和光学特性.结果表明:随膜厚增大,PbSe (200)晶面的择优取向显著增强,薄膜的结晶质量逐渐提高.此外,随薄膜厚度增加吸收边发生红移.膜厚为200nm、250 nm时,薄膜的禁带宽度为1.89 eV和1.60 eV;膜厚较大(500 nm及600 nm)时,带隙宽度减小至1.41 eV和1.34 eV,与太阳的光谱辐射更加匹配.因此,我们认为厚度较大的PbSe薄膜更适于用做太阳能电池的吸收层.     

Optical properties of tin sulphide (SnS) thin film estimated from transmission spectra

Thin films of tin sulphide (SnS) were deposited on tin oxide conducting glass substrates by thermal evaporation technique. The transmission spectrum of the SnS film in the wavelength range from 300 to 1100 nm has been obtained. X-ray diffraction has been used to determine the structure of the films. The film thickness and refractive index have been estimated from the transmission spectra. The results showed that the refractive index of the SnS thin films is thickness independent in the wavelength range 590 ≤ λ ≤ 1100 nm and found to be ~ 1.72. This result indicates that the SnS thin films are homogeneous and isotropic. The energy band gaps were found to be between 1.06 and 1.32 eV, which is in good agreement with literature values. The energy dependence of the obtained refractive index is also investigated.     

Characterization of As-Se-Tl films near infrared region

?Amorphous chalcogenide of As-Se-Tl glassy alloys was prepared by melt quenching technique. Films were deposited on a transparent glass substrate using thermal evaporation technique. The optical characterization of thin As-Se-Tl films was studied by the analysis of transmission spectra, measured at normal incidence, in the spectral range 200-3000. The envelope method, proposed by Swanepoel, is a commonly used method for studying optical properties of films with uniform and non uniform thickness. Thickness values as well as optical constants, refractive index, Dispersion energy, Urbach and static refractive index or infinite wave length dielectric constant, are calculated using Wemple-DiDomenico model near infrared region using the envelopes of the transmittance spectrum of the films. The values of optical constants: absorption coefficient, Urbach tail, refractive index etc. have been determined. Urbach tail is estimated using Tauc's extrapolation and is found to increase from 0.69 to 0.91 eV with the Tl addition. This behavior of Urbach tail is interpreted in terms of Tauc's Model. Other optical constants are interpreted in terms of Wemple-DiDomenico model, chemical bond approach, electro-negativity difference of the atoms involved and cohesive energy of the system.     

Refractive index,band gap and oscillator parameters of amorphous GaSe thin films

GaSe thin films are obtained by evaporating GaSe crystals onto ultrasonically cleaned glass substrates kept at room temperature under a pressure of ∼10^–5 Torr. The X‐ray analysis revealed that these films are of amorphous nature. The reflectance and transmittance of the films are measured in the incident photon energy range of 1.1–3.0 eV. The absorption coefficient spectral analysis revealed the existence of long and wide band tails of the localized states in the low absorption region. The band tails width is calculated to be 0.42 eV. The analysis of the absorption coefficient in the high absorption region revealed an indirect forbidden band gap of 1.93 eV. The transmittance analysis in the incidence photon wavelength range of 500–1100 nm allowed the determination of refractive index as function of wave length. The refractive index–wavelength variation leads to the determination of dispersion and oscillator energies as 31.23 and 3.90 eV, respectively. The static refractive index and static dielectric constant were also calculated as a result of the later data and found to be 9.0 and 3.0, respectively. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optical and structural properties of lead iodide thin films prepared by vacuum evaporation method

Thermally processed lead iodide (PbI₂) thin films were prepared by the vacuum evaporation method in a constant ambient. Measured thickness of the film was verified analytically from the optical transmittance data in a wavelength range between 300 and 1600 nm. From the Tauc relation for the non‐direct inter band transition, the optical band gap of the film was found to be 2.58 eV for film thickness 300 nm. X‐ray diffraction analysis confirmed that PbI₂ films are polycrystalline, having hexagonal structure. The low fluctuation in Urbach energy indicates that the grain size is quite small. The present findings are in agreement with the other results. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and characterization of manganese sulphide thin films deposited by spray pyrolysis

Manganese sulphide (MnS) thin films have been deposited onto glass substrate by a low cost spray‐pyrolysis technique at 220 °C. The as‐deposited MnS thin films have been characterized using scanning electron microscopy (SEM), energy dispersive X‐ray (EDX) spectroscopy, atomic force microscopy (AFM), X‐ray diffraction, UV visible spectroscopy and photo electrochemical (PEC) measurement. The SEM and AFM images showed that the MnS thin films were well covered onto the substrate surface. The as‐deposited raw thin film was found to be amorphous in nature and perfectly crystalline phase after annealing the sample. Optical band gap of the MnS thin films was found to vary from 3.1 to 3.21 eV and the band gap decreases with the increase in film thickness. Optical constants such as refractive index, extinction coefficient have been evaluated using reflectance and absorbance data. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Microstructure and optical properties of (Pb,Ca)TiO3 films grown on Si(1 0 0) substrates by a simple sol-gel process

Amorphous and polycrystalline (Pb_0.76Ca_0.24)TiO₃ (PCT) thin films deposited on an Si(1 0 0) substrate have been prepared by a simple sol-gel process. The microstructure and surface morphologies of the thin films have been studied by X-ray diffraction (XRD) and atomic force microscopy (AFM). The polycrystalline PCT film on the Si(1 0 0) substrate has a tetragonal perovskite structure with grain size from 60 to 110 nm. AFM reveals smooth surfaces and root mean square (rms) roughness of 0.17 and 4.4 nm for amorphous and polycrystalline films, respectively. The refractive index n and extinction coefficient k of the amorphous and polycrystalline thin films was obtained by spectroscopic ellipsometry as a function of the photon energy in the range from 2.0 to 5.4 eV. The maximum n and direct bandgap energies of amorphous and polycrystalline thin films were 2.66 and 4.11 eV, 2.64 and 3.84 eV, respectively.     

Influence of thermoannealing on crystallinity and optical properties of Sb2S3 thin films

Sb₂S₃ thin films are obtained by evaporating of Sb₂S₃ powder onto glass substrates maintained at room temperature under pressure of 2×10^‐5 torr. The composition of the thin films was determined by energy dispersive analysis of X‐ray (EDAX). The effect of thermal annealing in vacuum on the structural properties was studied using X‐ray diffraction (XRD) technique and scanning electron microscopy (SEM). The as‐deposition films were amorphous, while the annealed films have an orthorhombic polycrystalline structure. The optical constants of as‐deposited and annealed Sb₂S₃ thin films were obtained from the analysis of the experimental recorded transmission spectral data over the wavelength range 400‐1400 nm. The transmittance analysis allowed the determination of refractive index as function of wavelength. It was found that the refractive dispersion data obeyed the single oscillator model, from which the dispersion parameters (oscillator energy, E₀, dispersion energy, E_d) were determined. The static refractive index n(0), static dielectric constant, ε_∞, and optical band gap energy, E_g, were also calculated using the values of dispersion parameters. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Influence of annealing on the physical properties of filtered vacuum arc deposited tin oxide thin films

Tin oxide (SnO₂) thin films were deposited on UV fused silica (UVFS) substrates using filtered vacuum arc deposition (FVAD). During deposition, the substrates were at room temperature (RT). As-deposited films were annealed at 400 and 600 °C in Ar for 30 min. The film structure, composition, and surface morphology were determined as function of the annealing temperature using X-ray diffraction (XRD), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The XRD patterns of the SnO₂ thin films deposited on substrates at RT indicated that the films were amorphous, however, after the annealing the film structure became polycrystalline. The grain size of the annealed films, obtained from the XRD analysis, increased with the annealing temperature, and it was in the range 8-34 nm. The AFM analysis of the surface revealed an increase in the film surface average grain size from 15 nm to 46 nm, and the surface roughness from 0.2 to 1.8 nm, as function of the annealing temperature. The average optical transmission of the films in the visible spectrum was >80%, and increased by the annealing ∼10%. The films’ optical constants in the 250-989 nm wavelength range were determined by variable angle spectroscopic ellipsometry (VASE). The refractive indexes of as-deposited and annealed films were in the range 1.83-2.23 and 1.85-2.3, respectively. The extinction coefficients, k(λ), of as-deposited and annealed films were in the range same range ∼0-0.5. The optical energy band gap (E_g), as determined by the dependence of the absorption coefficient on the photon energy at short wavelengths, increased with the annealing temperature from 3.90 to 4.35 eV. The lowest electrical resistivity of the as-deposited tin oxide films was 7.8 × 10⁻³ Ω cm, however, film annealing resulted in highly resistive films.     

Optical properties of thermally evaporated CdS thin films

CdS thin films of varying thicknesses were deposited on cleaned glass substrates at room temperature by thermal evaporation technique in a vacuum of about 2 x 10^‐5 torr. UV‐VIS spectra of the films were studied using the optical transmittance measurements which were taken in the spectral region from 300 nm to 1100 nm. The absorbance and reflectance spectra of the films in the UV‐VIS region were also studied. Optical constants such as optical band gap, extinction coefficient, refractive index, optical conductivity and complex dielectric constant were evaluated from these spectra. All the films were found to exhibit high transmittance (∼ 60 ‐ 93 %), low absorbance and low reflectance in the visible/near infrared region from ∼ 500 nm to 1100 nm. The optical band gap energy was found to be in the range 2.28 – 2.53 eV. All the films annealed at 300°C for 4 hours in vacuum (∼ 10^‐2 torr) showed a decrease in the optical transmittance with its absorption edge shifted towards the longer wavelength, leading to the result that the optical band gap decreases on annealing the films. Also, on annealing crystallinity of the films improves, resulting in decrease in the optical transmittance. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Influence of gamma radiation on the absorption spectra and optical energy gap of Li‐ doped ZnO thin films

We have studied the effect of subsequent gamma (γ) irradiation on the absorption spectra and the optical energy gap of ZnO thin films doped with Li (ZnO:Li). The optical transmission (T) and optical reflection (R) in the wavelength range 190∼800 nm of films deposited at 300 °C on sapphire, MgO or quartz substrates were measured. The dependence of the absorption coefficient α on photon energy hν was determined as a function of γ‐doses. The films show direct allowed interband transition that influenced by the gamma doses. Both the optical energy gap E^opt_g and the absorption coefficient (α) were found to be γ‐dose dependent. The results can be discussed on the basis of γ‐irradiation‐induced defects in the film and on the film structure. The absorption coefficient exhibits exponential dependence on photon energy obeying Urbach's rule in the absorption edge. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)