Characterization of nanocrystalline cadmium telluride thin films grown by successive ionic layer adsorption and reaction (SILAR) method

Structural, electrical and optical characteristics of CdTe thin films prepared by a chemical deposition method, successive ionic layer adsorption and reaction (SILAR), are described. For deposition of CdTe thin films, cadmium acetate was used as cationic and sodium tellurite as anionic precursor in aqueous medium. In this process hydrazine hydrate is used as reducing agent and NH₄OH as the catalytic for the decomposition of hydrazine. By conducting several trials optimization of the adsorption, reaction and rinsing time duration for CdTe thin film deposition was done. In this paper the structural, optical and electrical properties of CdTe film are reported. The XRD pattern shows that films are nanocrystalline in nature. The resistivity is found to be of the order of 411 × 10³ Ω-cm at 523 K temperature with an activation energy of ∼ 0.2 eV. The optical absorption studies show that films have direct band gap (1.41 eV).     

连续式离子层吸附与反应法沉积CuSCN薄膜及其微观结构、光学特性研究

采用乙二醇作溶剂,以连续式离子层吸附与反应法(SILAR)实现硫氰酸亚铜(CuSCN)薄膜在ITO、TiO2薄膜以及玻璃衬底上的沉积.通过X射线衍射、扫描电镜和紫外-可见光透过谱等手段表征薄膜结晶性、表面和断面微观形貌以及光学特性.结果表明,衬底以及溶剂性质均对SILAR法薄膜沉积过程存在重要影响.ITO衬底上获得的CuSCN薄膜更为致密,呈结晶态,而TiO2薄膜衬底上的CuSCN薄膜主要由颗粒组成,为非晶态.随沉积次数增加,薄膜表面粗糙度增大,光学透过率逐渐下降.在优化条件下(ITO衬底,20次沉积循环),所得CuSCN薄膜表面致密均匀,可见光透过率约60%.     

Growth of zinc peroxide (ZnO2) and zinc oxide (ZnO) thin films by the successive ionic layer adsorption and reaction – SILAR – technique

Zinc peroxide, ZnO₂, thin films were grown by successive ionic layer adsorption and reaction (SILAR) technique at room temperature and normal pressure. The thin films were grown on glass, quartz, silicon, on poly(vinyl chloride) and polycarbonate substrates. The precursors used for ZnO₂ films were diluted aqueous solutions of ZnCl₂ complexed with ethylenediamine for cation and H₂O₂ for anion constituent of the film. The zinc peroxide film could be decomposed to zinc oxide by annealing in air or in vacuum. The as-grown films were polycrystalline, or amorphous and the annealed films were amorphous on all substrate materials. According to scanning electron microscopy images the films were uniform and homogeneous. The films were also characterized by UV spectroscopy.     

Growth of Cu thin films by the successive ionic layer adsorption and reaction (SILAR) method

Copper thin films were grown on reduced indium tin oxide, molybdenum and polymer substrates using successive ionic layer adsorption and reaction (SILAR) method. Copper films were grown sequentially in a controlled way using simple copper salt and basic solution of formaldehyde as precursors. The copper films were polycrystalline with no preferred orientation as characterised by X-ray diffraction. On all substrates, the growth was clearly island growth in the beginning but after the whole surface was covered, the growth was more homogeneous.     

连续离子层吸附与反应法(SILAR)生长ZnO多晶薄膜的研究

采用连续离子层吸附与反应法(SILAR),以锌氨络离子([Zn(NH₃)₄]²⁺)为前驱体溶液,在玻璃衬底上沉积了ZnO薄膜,以XRD和SEM等手段分析了薄膜的晶体结构和表面、断面形貌,考察了空气气氛下的退火过程对ZnO薄膜晶体结构与微观形貌的影响,并初步探讨了以SILAR方法沉积ZnO薄膜的机理.结果表明,经200次SILAR沉积循环,所得ZnO薄膜为红锌矿结构的多晶薄膜,沿<002>方向择优生长;薄膜表面致密、光滑均匀,厚度约800nm.退火处理使ZnO薄膜氧缺位减少,晶粒沿c轴取向增强;随退火温度升高,锌间隙原子增加;500℃退火时,ZnO薄膜发生再结晶.减小前驱体溶液的[NH₃·H₂O]/[Zn²⁺]比率可提高ZnO薄膜生长速率.     

Characterization of cadmium sulphide thin films prepared by successive ionic layers adsorption and reaction method

Cadmium sulfide (CdS) thin films were deposited on glass substrate at room temperature by successive ionic layer adsorption and reaction method (SILAR). The deposition parameters such as rinsing time, rinsing cycle and concentration of precursor solution were varied during the preparation of the samples. The structural characterization and optical characterization were carried out. The deposited films by lower growth rate and lower precursor concentration solutions were having mixed hexagonal and cubic phases. Thickness dependence of the optical band gap energy was evaluated and it varies from 2.46 to 2.32 eV in the thickness range 38–330 nm.     

CuSCN薄膜的室温液相沉积及其光学性能

采用连续离子层吸附与反应(SILAR)方法, 在室温液相条件下(20～25℃)制备了沉积于玻璃衬底上的CuSCN半导体薄膜, 以X射线衍射、扫描电镜、光学透过谱考察了所得薄膜的晶体结构、微观表面断面形貌和光学性能, 探讨了影响CuSCN薄膜沉积的关键因素. 结果表明, 所得薄膜具有明显结晶性及沿c轴择优生长趋势, 表面致密、均匀, 分别由50～100nm的较大颗粒和20～30nm的小颗粒紧密堆聚而成; 薄膜在400～800nm波段的透过率为50%～70%, 光学禁带宽度为3.94eV. CuSCN薄膜的沉积过程受铜前驱液中S2O32-与Cu2+的摩尔比、衬底漂洗方式和生长温度等因素影响显著, 高络离子浓度、多次沉积反应后再进行衬底漂洗、以及室温生长条件有利于得到高质量的CuSCN薄膜.     

Enhancement of photosensitivity by annealing in Bi2S3 thin films grown using SILAR method

Bi₂S₃ thin films were grown by successive ionic layer adsorption and reaction method (SILAR) onto the glass substrates at room temperature. The as prepared thin film were annealed at 250 °C in air for 30 min. These films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and electrical measurement systems. The X-ray diffraction patterns reveal that Bi₂S₃ thin film have orthorhombic crystal structure. SEM images showed uniform deposition of the material over the entire glass substrate. The optical energy band gap observed to be decreased from 1.69 to 1.62 eV for as deposited and annealed films respectively. The I–V measurement under dark and illumination condition (100 W) show annealed Bi₂S₃ thin film gives good photoresponse as compared to as deposited thin film and Bi₂S₃ thin film exhibits photoconductivity phenomena suggesting its useful in sensors device. The thermo-emf measurements of Bi₂S₃ thin films revealed n-type electrical conductivity.     

Near-infrared responsive PbS-sensitized photovoltaic photodetectors fabricated by the spin-assisted successive ionic layer adsorption and reaction method

A PbS-sensitized photovoltaic photodetector responsive to near-infrared (NIR) light was fabricated by depositing monolayered PbS nanoparticles on a mesoporous TiO(2) (mp-TiO(2)) film via the spin-assisted successive ionic layer adsorption and reaction (SILAR) method. By adjusting the size and morphology of the PbS nanoparticles through repeated spin-assisted SILAR cycles, the PbS-sensitized photovoltaic photodetector achieved an external quantum efficiency of 9.3% at 1140 nm wavelength and could process signals up to 1 kHz.     

Fabrication of CdS/SnS heterostructured device using successive ionic layer adsorption and reaction deposited SnS

In the present work successive ionic layer adsorption and reaction (SILAR) method has been employed for the growth of SnS films on chemical bath deposited CdS thin films. The as-grown and post annealed CdS/SnS heterostructures were investigated under dark and illuminated conditions. It has been observed that annealing improves the quality of the device. This paper presents the attempt towards realizing SnS based heterostructured devices using SnS films grown by SILAR technique.     

Some studies on successive ionic layer adsorption and reaction (SILAR) grown indium sulphide thin films

Indium sulphide (In₂S₃) thin films were grown on amorphous glass substrate by the successive ionic layer adsorption and reaction (SILAR) method. X-ray diffraction, optical absorption, scanning electron microscopy (SEM) and Rutherford back scattering (RBS) were applied to study the structural, optical, surface morphological and compositional properties of the indium sulphide thin films. Utilization of triethanolamine and hydrazine hydrate complexed indium sulphate and sodium sulphide as precursors resulted in nanocrystalline In₂S₃ thin film. The optical band gap was found to be 2.7 eV. The film appeared to be smooth and homogeneous from SEM study.     

Preparation and characterization of amorphous manganese sulfide thin films by SILAR method

Manganese sulfide thin films were deposited by a simple and inexpensive successive ionic layer adsorption and reaction (SILAR) method using manganese acetate as a manganese and sodium sulfide as sulfide ion sources, respectively. Manganese sulfide films were characterized for their structural, surface morphological and optical properties by means of X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis and optical absorption measurement techniques. The as-deposited film on glass substrate was amorphous. The optical band gap of the film was found to be thickness dependent. As thickness increases optical band gap was found to be increase. The water angle contact was found to be 34°, suggesting hydrophilic nature of manganese sulfide thin films. The presence of Mn and S in thin film was confirmed by energy dispersive X-ray analysis.     

Chemically deposited TiO2/CdS bilayer system for photoelectrochemical properties

In the present investigation, TiO₂, CdS and TiO₂/CdS bilayer system have been deposited on the fluorine doped tin oxide (FTO) coated glass substrate by chemical methods. Nanograined TiO₂ was deposited on FTO coated glass substrates by successive ionic layers adsorption and reaction (SILAR) method. Chemical bath deposition (CBD) method was employed to deposit CdS thin film on pre-deposited TiO₂ film. A further study has been made for structural, surface morphological, optical and photoelectrochemical (PEC) properties of FTO/TiO₂, FTO/CdS and FTO/TiO₂/CdS bilayers system. PEC behaviour of FTO/TiO₂/CdS bilayers was studied and compared with FTO/CdS single system. FTO/TiO₂/CdS bilayers system showed improved performance of PEC properties over individual FTO/CdS thin films.     

Optical and structural properties of zinc oxide films with different thicknesses prepared by successive ionic layer adsorption and reaction method

In this work, zinc oxide semiconducting films belonging to the II-VI group have been produced by successive ionic layer adsorption and reaction (SILAR) method on glass substrates with 10, 15, 20 and 25 cycles at room temperature. Following the deposition, the samples were dried in air at 400 °C for 1 h. The films were characterized by X-ray diffraction, field emission scanning electron microscopy and optical absorption measurement techniques. The X-ray diffractions of the films showed that they are hexagonal in structure. The crystallite size of ZnO films varied between 34 and 38 nm accordingly with the number of SILAR cycles. The material has exhibited direct band gap transition with the band gap values lying in the range between 3.13 and 3.18 eV. The red shift is observed in the absorption edge as the cycles increased. Transmission of the films decreased from 65 to 40% with increasing the number of cycles.     

Analysis of sulphur deficiency defect prevalent in SILAR-CdS films

When cadmium sulphide (CdS) films are deposited using successive ionic layer adsorption and reaction (SILAR) process, a sulphur deficiency defect is always observed. The reason for this defect is addressed in the present work, by systematically analyzing the increasing pattern of Cd²⁺ions available in the anionic solution bath during the SILAR dipping cycles. The variation of the Cd²⁺ ion concentration in the anionic solution bath with respect to the number of cycles is analyzed in detail using inductive coupled plasma (ICP) analysis. Moreover, the corresponding sulphur deficiency generated in the CdS thin films is also analyzed using the energy dispersive X-ray analysis profiles, appropriately correlated with the ICP results. The optical transmittance and the thickness measurements are carried out as supplementary studies to support the analysis on the sulphur deficiency. The obtained results may be useful for rectifying this sulfur deficiency defect which is commonly occurred in CdS films deposited using chemical bath deposition as well as SILAR methods.     

Formation of rod-crystals on CuInSe2 thin films by SILAR method using CH3-(CH2)11-C6H4-SO3Na surfactant

The formation of rod-crystals was observed on CuInSe₂ thin films prepared by successive ionic layer adsorption and reaction (SILAR) method using sodium dodecylbenzene sulfonate (SDBS) as directing agent. Rod-crystals appeared on the surface of CuInSe₂ thin film when adding SDBS into cationic precursor solution. FESEM, EDS, XRD and HRTEM were used to characterize the rod-crystals. The length of rod-crystals has a proportional relationship with SDBS amounts in the given scope of 0.001-0.01 mol/L. The stoichiometry of rod was close to 1:1:2 of CuInSe₂, and rod growth of partially preferential orientation along [112] was observed. The growth of rod could be explained by steric hindrance effects of SDBS adsorbed on the inorganic deposit surface.     

超声辅助SILAR法生长纳米晶ZnO多孔薄膜及其光学性能研究

将超声辐照技术引入连续离子层吸附与反应(SILAR)法,提出超声辅助连续离子层吸附与反应(UA-SILAR)液相成膜技术.以锌氨络离子([Zn(NH₃)₄]²⁺)溶液为前驱体,在90℃下沉积得到ZnO薄膜,对其晶体结构,微观形貌、透过光谱和光致发光性能进行表征, 并考察了超声辐照和沉积循环次数对薄膜形貌、结构和光学特性的影响.结果表明,所得薄膜由彼此交联、尺寸均匀的ZnO晶粒组成,呈现典型的多孔特征,同时具有高结晶性和强c轴取向性.由于多孔结构对入射光的散射作用,薄膜在可见光区具有低透射率(约20%);在紫外光激发下,薄膜具有较强的近带边发射和很弱的蓝带发射,体现出薄膜较高的光学质量;薄膜生长过程中超声辐照的引入可对薄膜的结晶性能和微观结构产生显著的影响.     

Fabrication of PbS nanoparticle-sensitized TiO₂ nanotube arrays and their photoelectrochemical properties

TiO(2) nanotube arrays (NTAs) are modified with PbS nanoparticles by successive ionic layer adsorption and reaction (SILAR) or electrodeposition, with an aim towards tuning the photoelectrochemical cell to the visible region. The PbS modification of the TiO(2) NTAs results in an increase in the visible light adsorption, however the increase in photocurrent is dependent on the modification method. PbS/TiO(2) NTAs prepared by SILAR and electrodeposition show, respectively, photocurrents of 11.02 and 5.72 mA/cm(2). The increase in photocurrent is attributed to enhanced charge separation efficiency and improved electron transport.     

Room temperature deposition of ZnSe thin films by successive ionic layer adsorption and reaction (SILAR) method

The zinc selenide (ZnSe) thin films are deposited onto glass substrate using relatively simple and inexpensive successive ionic layer adsorption and reaction (SILAR) method. The films are deposited using zinc acetate sodium selenosulphate precursors. The concentration, pH, immersion and rinsing times and number of immersion cycles have been optimized to obtain good quality ZnSe thin films. The X-ray diffraction (XRD) study and scanning electron microscopy (SEM) studies reveals nanocrystalline nature alongwith some amorphous phase present in ZnSe thin films. Energy dispersive X-ray (EDAX) analysis shows that the films are Se deficient. From optical absorption data, the optical band gap ‘E_g’ for as-deposited thin film was found to be 2.8 eV and electrical resistivity in the order of 10⁷ Ω cm.     

Influence of Mn dopant concentration on film thickness,structural, morphological,compositional and optical properties of zinc oxide thin films

Thin films of zinc oxide (ZnO) and manganese doped zinc oxide (ZnO:Mn) have been prepared on glass substrates by the method of successive ionic layer adsorption reaction (SILAR) technique. X-ray diffraction pattern revealed that the prepared films found to exhibit hexagonal structure with preferential orientation along (101) plane. Scanning electron microscopic analysis showed the appearance of needle shaped flower like grains for ZnO and ZnO:Mn. The value of band gap is found to be in the range between 3.01 and 3.26 eV. Photoluminescence spectroscopic analysis showed that increase in value of peak intensity is observed for ZnO:Mn than ZnO.