Influence of ultrsonification in CdS thin film deposition in PCD technique

CdS thin films are successfully deposited from aqueous solutions by photochemical reactions. CdS thin films are deposited on a glass substrate only in the UV illuminated region by heterogeneous nucleation. Ultrasonic vibrations are used to stir the solution because ultrasonic waves can drive chemical reactions such as oxidation, reduction and decomposition. The nature of the as-deposited and annealed CdS thin films was studied using XRD, Hall measurements and AES. The surface morphology of the film has been studied using a scanning electron microscope. AES and SEM analysis on as-deposited CdS thin film showed that the surface contains less impurity and change in morphology under the influence of ultrosonic vibrations.     

Pulsed laser deposition of a thin conjugated-polymer film

Thin films of poly(3-octylthiophene), P3OT, were deposited by pulsed laser ablation method. Infrared spectroscopy indicates that the major chemical structure of P3OT survived the ablative process. In addition, the films exhibit enhanced linear and non-linear optical responses as compared with the spin-coated P3OT films. Our results demonstrate the potential of laser ablation in producing π-conjugated polymer films of high quality.     

射频溅射两步法制备立方氮化硼(c-BN)薄膜

~~射频溅射两步法制备立方氮化硼(c-BN)薄膜@冯贞健$北京工业大学教育部新型功能材料重点实验室!北京100022 @邢光建$北京工业大学教育部新型功能材料重点实验室!北京100022 @陈光华$北京工业大学教育部新型功能材料重点实验室!北京100022 @于春娜$北京工业大学教育部新型功能材料重点实验室!北京100022 @荣延栋$北京工业大学教育部新型功能材料重点实验室!北京100022~~~~~~~~     

Investigation of CuInS2 thin film formation by a low-temperature chemical deposition method

Copper indium disulfide (CuInS(2), CIS) thin films were prepared by an alternative solution-based coating process adapted from the well-established aqueous metal salt/thiourea precursor system. The temperature for the decomposition of the precursors and the formation of CIS was lowered significantly to 130 °C by using the strongly coordinating solvent pyridine instead of the commonly used water. In addition, the influence of different annealing temperatures and concentrations of thiourea (TU) in the precursor solution on the obtained CIS samples was investigated. The films possess highly beneficial properties for photovoltaic applications, showing a chalcopyrite crystal structure, a high optical absorption (>10(4) cm(-1)) and an optical band gap between 1.45 and 1.51 eV. Chemical and morphological changes during the thin film formation were detected and explained by time-resolved simultaneous grazing incident small- and wide-angle X-ray scattering (GISAXS, GIWAXS) measurements, scanning electron microsccopy (SEM) and simultaneous thermogravimetry/mass spectroscopy (TG/MS).     

Chemical vapor deposition growth of monolayer MoSe2 nanosheets

The synthesis of two-dimensional （2D） layered materials with controllable thickness is of considerable interest for diverse applications. Here we report the first chemical vapor deposition growth of single- and few-layer MoSe2 nanosheets. By using Se and MoO3 as the chemical vapor supply, we demonstrate that highly crystalline MoSe2 can be directly grown on the 300 nm SiO2/Si substrates to form optically distinguishable single- and multi-layer nanosheets, typically in triangular shaped domains with edge lengths around 30 btm, which can merge into continuous thin films upon further growth. Micro-Raman spectroscopy and imaging was used to probe the thickness-dependent vibrational properties. Photoluminescence spectroscopy demonstrates that MoSe2 monolayers exhibit strong near band edge emission at 1.55 eV, while bilayers or multi-layers exhibit much weaker emission, indicating of the transition to a direct band gap semiconductor as the thickness is reduced to a monolayer.     

Substrate preparation for thin film deposition—a survey

Surface preparation is an integral part of any thin film deposition process. As the technological demands on films and coatings increase, the need for better and more reproducible surface preparation techniques is also increased. There is a wide variety of approaches to surface preparation and each film-substrate couple and function require specific development. This paper outlines the problems to be considered and some general approaches to surface preparation technologies.     

Nebulized spray deposition of PLT thin film

Films of lead lanthanum titanate (PLT) are deposited on n-type (100) Si and Pt/TiO2/Ti/ SiO2/(100)Si substrates by using ultrasonic nebulized spray deposition. In this work, Pb(CH3COO)2 3H2O, La(NO3)3 6H2O, Ti(i-C3 H7O)4 are used as reactants. Experimental results reveal that the films are transformed from tetragonal to nearly cubic as the lanthanum content increases. The refractive index and grain size decrease with the increase of La content in the films. From C-V and I-V measurements of the Al/PLT/n-Si (MIS) and Pt/PLT/Pt/TiO2/Ti/ SiO2/n-Si (MIM) structures, the dielectric properties are determined. The permittivities are found to increase with the La content to a maximum value of about 275 and 530 for the MIS and MIM structures, respectively, and then decrease with further increase of La content for the films grown at 550°C. The results of I-V measurements indicate that the leakage currents of the MIS structure are higher than in the MIM structure. The P-E hysteresis loop became slimmer with the increase of La concentration due to lower tetragonality (c/a), and when the La content is higher than 20 mol %, the films behave like a normal dielectric.     

Characterization of the small molecule based organic thin film fabricated by electrospray deposition technique

A novel route for the fabrication of the SM based 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) organic thin film by electrospray deposition (ESD) technique has been presented in this paper. The tailoring of the film thickness was also performed by varying the number of deposition passes at a constant substrate speed. The structural and optical characterizations of the fabricated BCP thin film were thoroughly investigated. The energy gap of the fabricated thin film was measured to be 3.5 eV. Furthermore, the electrical performance of the BCP thin film was verified by performing current–voltage measurement of the prototype organic diode device having fabricated BCP film as a buffer layer. The current density–voltage characteristic curve of the organic device showed non linear diode like behavior, thereby confirming the proper interference established between organic diode adjacent layers. At low voltage, the device showed ohmic conduction, where as the space charged limited current and trap charge limited current mechanism have been found to be dominant in the fabricated organic device at higher voltage. Overall, the results suggest that the ESD approach will be promising for organic semiconductor device fabrication at low cost and with low material loss.     

Ion-based methods for optical thin film deposition

The optical properties of the dielectric oxide films SiO₂, Al₂O₃, TiO₂, ZrO₂, CeO₂ and Ta₂O₅ produced by ion-based techniques have been reviewed. The influence of ion bombardment during deposition is discussed in some detail and the various production techniques are described. Recent results on the deposition and properties of diamond-like carbon films are also reviewed. Finally, some examples of the practical applications of high quality dielectric oxide films are given.     

Electrospray droplet sources for thin film deposition

Electrospraying utilises electrical forces for liquid atomisation. Droplets obtained by this method are highly charged to a fraction of the Rayleigh limit. The advantage of electrospraying is that the droplets can be extremely small, down to the order of 10’s nanometres, and the charge and size of the droplets can be controlled to some extent be electrical means. Motion of the charged droplets can be controlled by electric field. The deposition efficiency of the charged spray on an object is usually higher than that for uncharged droplets. Electrospray is, or potentially can be applied to many processes in industry and in scientific instruments manufacturing. The paper reviews electrospray methods and devices, including liquid metal ion sources, used for thin film deposition. This technique is applied in modern material technologies, microelectronics, micromachining, and nanotechnology.     

Shallow bath chemical deposition of CdS thin film

Cadmium sulfide thin film was grown by shallow chemical bath deposition technique. This technique used a highly conducted hot plate to heat the substrate, while using a shallow bath for higher thermal gradients. As a result, large area uniformity could be achieved and the homogeneous nucleation was suppressed. More importantly, the solution used was greatly reduced, which is crucial for cost reduction in practice. The effects of temperature and shaking on the growth kinetics and film properties were investigated. The reaction activation energy was obtained to be 0.84 eV, and was not affected much by shaking indicating that the deposition is essentially reaction controlled. Furthermore, the films deposited at low or high temperature conditions had better photoconductivity.     

Optimization of deposition temperature of SILAR Cu-rich CuInS2 thin films

CuInS₂ (CIS) is studied widely as a promising absorber material for high efficient and low cost thin film solar cells. CIS thin films are prepared on soda lime glass substrates using Successive Ionic Layer Adsorption and Reaction (SILAR) technique at different deposition temperatures (40 to 70 °C). The structural, compositional and optical properties are studied with x-ray diffractometer, energy dispersive x-ray analyzer and spectrophotometer. The influence of the deposition temperature on the properties of CIS thin films is discussed in this paper in detail.     

Synthesis of hexagonal and cubic GaN thin film on Si (111) using a low-cost electrochemical deposition technique

Gallium nitride GaN thin films were deposited on Si (111) substrates using electrochemical deposition technique at 20 °C. SEM images and EDX results indicated that the growth of GaN films varies with the current density. XRD and Raman analyses showed the presence of hexagonal wurtzite and cubic zinc blende GaN phases with the crystallite size around 18-19 nm. Photoluminescence spectrum showed that the energy gaps of h-GaN/Si (111) and c-GaN/Si (111) were near 3.39 eV and 3.2 eV respectively at 300 K. Raman spectrum indicated the presence of mixed phonon modes of hexagonal and cubic GaN.     

Room-temperature deposition of amorphous titanium dioxide thin film with high refractive index by a filtered cathodic vacuum arc technique

Amorphous titanium dioxide (TiO2) thin film has been prepared by a filtered cathodic vacuum arc technique at room temperature. It was concluded from the core level of Ti 2p 3/2 (458.3 eV) and O 1s (529.9 eV) and their deviation in binding energy (deltaBE = 71.6 eV) that only one of Ti oxidation states, Ti4+, existed in the film and the film was of ideal stoichiometry. The film possessed high transmittance, which can reach as high as that of a quartz substrate, especially in the visible range, owing to its optical bandgap of 3.2 eV. The high refractive index (2.56 at 550 nm) and low extinction coefficient (approximately 10(-4) at 550 nm) suggested that the film had a high packing density and a low scattering-center concentration. These good optical properties implied the film prepared by this technique was a promising candidate for optical application. Besides, the film was found to transform in the structure from amorphous to anatase crystalline when it was annealed at 300 degrees C, as evidenced by Raman and x-ray diffraction.     

Morphological and structural analysis of nano-structured gold thin film on silicon by pulsed laser deposition technique

Structural and morphological investigations on optimized nano-structured gold thin film (under vacuum ∼10⁻³ Torr) are reported. The Au optimized thin film was deposited on 4 N polished and analytic grade p-type single crystal (111) Silicon wafer by pulsed laser deposition (PLD) technique, under a vacuum of about 10⁻³ Torr at room temperature. The space resolved dynamics of the plume is studied by analyzing CCD images of plume. Average size of deposited nanoparticles is along the preferred (111) orientation is ∼ 20 nm using PLD technique. The deposited film is non-uniform with particle size within the range of 6.19 nm-19.62 nm. There is decrease in the value of dislocation line density. XRD and SEM investigations support each other.