Annealing Temperature-Dependent Luminescence Color Coordination in Eu-Doped AlN Thin Films

AlN was used as a host material and doped with Eu grown on Si substrate by pulsed laser deposition (PLD) with low substrate temperature. The X-ray diffraction (XRD) data revealed the orientation and the composition of the thin film. The surface morphology was studied by scanning electron microscope (SEM). While raising the annealing temperatures from 300˚C to 900˚C, the emission was observed from AlN: Eu under excitation of 260 nm excitation. The photoluminescence (PL) was integrated over the visible light wavelength shifted from the blue to the red zone in the CIE 1931 chromaticity coordinates. The luminescence color coordination of AlN: Eu depending on the annealing temperatures guides the further study of Eu-doped nitrides manufacturing on white light emitting diode (LED) and full color LED devices.

Step-confined thin film growth via near-surface atom migration

Understanding of thin film growth mechanism is crucial for tailoring film growth behaviors,which in turn determine physicochemical properties of the resulting films.Here,vapor-growth of tungsten carbide overlayers on W(110)surface is investigated by real time low energy electron microscopy.The surface growth is strongly confined by surface steps,which is in contrast with overlayer growth crossing steps in a so-called carpet-like growth mode for example in graphene growth on metal surfaces.Density functional theory calculations indicate that the step-confined growth is caused by the strong interaction of the forming carbide overlayer with the substrate blocking cross-step growth of the film.Furthermore,the tungsten carbide growth within each terrace is facilitated by the supply of carbon atoms from near-surface regions at high temperatures.These findings suggest the critical role of near-surface atom diffusion and step confinement effects in the thin film growth,which may be active in many film growth systems.

Growth of HT-LiCoO2 thin films on Pt-metalized silicon substrates

Layered LiCoO2 （HT-LiCoO2） films were grown on Pt-metalized silicon （PMS） substrates and polished bulk nickel （PBN） substrates by pulsed laser deposition. The effects of substrate temperature, oxygen pressure, and substrate surface roughness on the microstructure of LiCoO2 films were investigated. It has been found that a higher substrate temperature and a higher oxygen pressure favor the formation of better crystallized and less lithium-deficient HT-LiCoO2 films. The HT-LiCoO2 film deposited on PBN substrates consists of large randomly orientated equiaxial grains, whereas on PMS substrate, it is made up of loosely packed highly [001] preferential orientated triangular shaped grains with the average grain size less than 100 nm. Electrochemical measurements show that the highly [001] preferentially orientated nanostructured HT-LiCoO2 thin film grown on PMS substrate has good structural stability upon lithium insertion/extraction and can deliver an initial discharge capacity of approximately 45μA·h·cm^-2·μm^-1 with a cycling efficiency of above 99% at the charge/discharge rate of 0.5 C.

Effect of growth temperature on morphology,structure and luminescence of Tb-doped BN thin films

This paper investigates the effect of growth temperature on morphology, structure and photoluminescence （PL） of Tb-doped boron nitride （BN） films grown by magnetron sputtering, and the relationships of growth-temperature- structure-PL by scanning electron microscopy, transmission electron microscopy and PL. The characteristic emission lines of the Tb^3＋ were observed in the PL spectra at room temperature. The 473-K-grown film is mainly consisted of amorphous BN particles. With the growth temperature increasing up to 1273 K, the amount of amorphous BN decreases, while the amount of turbostratic BN increases. Correspondingly, the PL intensities from the Tb^3＋ ions increase with the increase of temperature in the range of 473 1273 K.

Parallel computing for lattice Monte Carlo simulation of large-scale thin film growth

This paper proposes two viable computing strategies for distributed parallel systems: domain division with sub-domain overlapping and asynchronous communication. We have implemented a parallel computing procedure for simulation of Ti thin film growing process of a system with 1000 x 1000 atoms by means of the Monte Carlo (MC) method. This approach greatly reduces the computation time for simulation of large-scale thin film growth under realistic deposition rates. The multi-lattice MC model of deposition comprises two basic events: deposition, and surface diffusion. Since diffusion constitutes more than 90% of the total simulation time of the whole deposition process at high temperature, we concentrated on implementing a new parallel diffusion simulation that reduces communication time during simulation. Asynchronous communication and domain overlapping techniques are used to reduce the waiting time and communication time among parallel processors. The parallel algorithms we propose can simulate the thin film growth of a system with many more particles than before under realistic deposition rates, and can provide a more efficient means for computer simulation of thin film growth.

Kinetic Monte Carlo simulation of thin film growth

A three-dimensional kinetic Monte Carlo technique has been developed for simulating growth of thin Cu films. The model involves incident atom attachment, diffusion of the atoms on the growing surface, and detachment of the atoms from the growing surface. The related effect by surface atom diffusion was taken into account. A great improvement was made on calculation of the activation energy for atom diffusion based on a reasonable assumtion of interaction potential between atoms. The surface roughness and the relative density of the films were simulated as the functions of growth substrate temperature and film thickness. The results showed that there exists an optimum growth temperatureT opt at a given deposition rate. When the substrate temperature approaches toT opt, the growing surface becomes smoothing and the relative density of the films increases. The surface roughness minimizes and the relative density saturates atT opt. The surface roughness increases with an increment of substrate, temperature when the temperature is higher thanT opt.T opt is a function of the deposition rate and the influence of the deposition rate on the surface roughness depends on the substrate temperatures. The simulation results also showed that the relative density decreases with the increasing of the deposition rate and the average thickness of the film.

Induced growth of high quality ZnO thin films by crystallized amorphous ZnO

This paper reports the induced growth of high quality ZnO thin film by crystallized amorphous ZnO. Firstly amorphous ZnO was prepared by solid-state pyrolytic reaction, then by taking crystallized amorphous ZnO as seeds （buffer layer）, ZnO thin films have been grown in diethyene glycol solution of zinc acetate at 80 ℃. X-ray Diffraction curve indicates that the films were preferentially oriented [001] out-of-plane direction of the ZnO. Atomic force microscopy and scanning electron microscopy were used to evaluate the surface morphology of the ZnO thin film. Photoluminescence spectrum exhibits a strong ultraviolet emission while the visible emission is very weak. The results indicate that high quality ZnO thin film was obtained.

Growth Character of YBaCuO Thin Film Deposited by DC-planar Magnetron Sputtering

The growth character and microstructure of high-T_c supereonducting YBCO thin films deposited on vari- ous substrates have been studied by X-ray diffraction, TEM and SEM.The results show that when the substrate temperaturc is around 700～800℃ the films have a highly oriented texture with c-axis pependicular to the substrate. The structure of the single crystalline YBCO films grown epitaxially at optimal substrate tem- perature of 800℃ has been established by X-ray diffraction using Seemann-Bohlin geometry (SB). Brentano-Bragg geometry(BB),transmission Laue method and TEM. The lattice matching required for epitaxial growth is achievcd by azimuthal adjustment of the film plane with respect to the substrate plane. The sperior growth is demonstrated by film properties such as critical current density(2.4×10~6 A /cm^2,3.4× 10~6 A/cm^2 and 4.7×l0~6 A/cm^2) for films deposited on YSZ[(Zr(Y)O_2],SrTiO_3 and LaAIO_3 respectively at 77 K and zero fie1d.

The Research on Growth Temperature of Ge/Si Thin Films Grown by Magnetron Sputtering

The films of Ge and Si were grown on the substrate Si (100) by magnetron sputtering at 2.5 Pa Ar pressure.The growth temperature of films was 100℃,250℃,400℃and 550℃.The structure and composition were analysised by Raman scattering.The poly-crystal peak and crystal peak of Ge were observed in these films.The results indicate that the single crystal film of Ge was prepared at the substrate temperature of 400℃.The peak of acoustic phonons of Ge was 98 cm^(-1) and that of Si was 170 cm^(-1).

Thin-film growth behavior of non-planar vanadium oxide phthalocyanine

The thin film properties of organic semiconductors are very important to the device performance.Herein,non-planar vanadyl phthalocyanine(VOPc)thin films grown on rigid substrates of indium tin oxide,silicon dioxide,and flexible substrate of kapton by organic molecular beam deposition under vacuum conditions are systematically studied via atomic force microscopy and x-ray diffraction.The results clearly reveal that the morphology and grain size are strongly dependent on the substrate temperature during the process of film deposition.Meanwhile,the VOPc films with the structure of phase I or phase II can be modulated via in situ annealing and post-annealing temperature.Furthermore,the crystalline structure and molecular orientation of vapor-deposited VOPc can be controlled using molecular template layer 3,4,9,10-perylenetetracarboxylic dianhydride(PTCDA),the VOPc film of which exhibits the phase I structure.The deep understanding of growth mechanism of non-planar VOPc film provides valuable information for controlling structure-property relationship and accelerates the application in electronic and optoelectronic devices.

Effect of Oxygen Partial Pressure on Epitaxial Growth and Properties of Laser-Ablated AZO Thin Films

Al-doped ZnO（AZO） thin films were grown on c-sapphire substrates by laser ablation under different oxygen partial pressures（P_（O2））.The effect of P_（O2） on the crystal structure,preferred orientation as well as the electrical and optical properties of the films was investigated.The structure characterizations indicated that the as-grown films were single-phased with a wurtzite ZnO structure,showing a significant c-axis orientation.The films were well crystallized and exhibited better crystallinity and denser texture when deposited at higher P_（O2）.At the optimum oxygen partial pressures of 10- 15 Pa,the AZO thin films were epitaxially grown on c-sapphire substrates with the（0001） plane parallel to the substrate surface,i e,the epitaxial relationship was AZO（000 1） // A1_2O_3（000 1）.With increasing P_（O2）,the value of Hall carrier mobility was increased remarkably while that of carrier concentration was decreased slightly,which led to an enhancement in electrical conductivity of the AZO thin films.All the films were highly transparent with an optical transmittance higher than 85%.

Effect of Concentration on the Optical and Solid State Properties of CoO Thin Films Deposited Using the Aqueous Chemical Growth (ACG) Method

Thin films of Cobalt(II) Oxide were deposited from equimolar concentrations of Cobalt Chloride, and Hexamethylenetetramine on clean glass substrates using the Aqueous Chemical Growth method in order to determine the effect of precursor concentration on their optical and solid state properties. The analytical tools used for the study include, Rutherford Back Scattering (RBS) spectroscopy for elemental analysis and determination of film thickness, X-Ray Difftraction (XRD) for crystallographic structure, a UV-VIS spectrophotometer for optical and other solid state properties and a photomicroscope for photomicrographs. The results indicate that an increase in the concentration of precursor materials makes ACG CoO thin film a better absorber of ultraviolet radiation, a better transmitter of infra-red radiation, a reflector of visible radiation and a material having an increased band gap. The ACG CoO thin film deposited from 0.1 M precursor concentration was found to be a suitable material for the construction of thermographic devices, poultry houses etc. It can also serve as window layer in solar cells among other optoelectronic applications.

Growth of MgO Thin Film on Silicon Substrate by MOCVD

Highly oriented MgO(111)and MgO(100)thin films have been deposited on Si(111)and Si(100)substrates by using Low Pressure MOCVD(LPMOCVD).Magnesium 2,4-pentanedionate was used as the source ma- terial.The films have a very smooth surface morphology and optical transparency with an index of refraction of 1.71(632.8 nm).Typical growth rate of the films is 1.0 μm/h.The data of X-ray diffraction analysis indi- cate that the films are fully textured with(111)and(100)orientation perpendicular to the substrate surface respectively.The main parameters having influence on the deposition are the substrate temperature,the total pressure in the reaction chamber,the reaction gases and its flowrate.

Effect of initial precursor concentration on TiO_2 thin film nanostructures prepared by PCVD system

TiO2 thin film was prepared on Si substrate by plasma chemical vapor deposition （PCVD） system and the morphologies of ZiO2 thin film were controlled by adjusting the initial precursor concentration. As the initial titanium tetra-isopropoxide （TTIP） concentration increases in PCVD reactor, the shapes of TiO2 particles generated in PCVD reactor change from the spherical small-sized particles around 20 nm and spherical large-sized particles around 60 nm to aggregate particles around 100 nm. The TiO2 particles with different shapes deposit on the substrate and become the main building blocks of resulting TiO2 thin film. We observed the TiO2 thin film with smooth morphology at low initial TTIP concentration, granular morphology at medium initial TTIP concentration, and columnar morphology at high initial TTIP concentration. It is proposed that we can prepare the TiO2 thin film with controlled morphologies in one-step process just by adjusting the initial precursor concentration in PCVD .

Studies on the Thin Film of TiO_2, Fe_2O_3 and SnO_2 by the Organometallic-CVD Technique

Pure TiO;,Fe;O;and SnO;are wide-bandgap semiconductors.Their films have high transparency in visible spectral region.These oxide films have been applied to electronics,optoelectronics, solar cells and display devices.A variety of techniques including reactive sputtering,reactive evaporation, ion-beam evaporation and chemical vapor deposition, and hydrolyses of the respective halides or alkoxides have been employed for the growth of thin films of TiO;,Fe;O;and SnO;.In

Influence of reaction gas flows on the properties of SiGe:H thin film prepared by plasma assisted reactive thermal chemical vapour deposition

A new preparing technology, very high frequency plasma assisted reactive thermal chemical vapour deposition （VHFPA-RTCVD）, is introduced to prepare SiGe：H thin films on substrate kept at a lower temperature. In the previous work, reactive thermal chemical vapour deposition （I^TCVD） technology was successfully used to prepare SiGe：H thin films, but the temperature of the substrate needed to exceed 400℃. In this work, very high frequency plasma method is used to assist RTCVD technology in reducing the temperature of substrate by largely enhancing the temperature of reacting gases on the surface of the substrate. The growth rate, structural properties, surface morphology, photo- conductivity and dark-conductivity of SiGe：H thin films prepared by this new technology are investigated for films with different germanium concentrations, and the experimental results are discussed.

Spontaneous Hillock Growth on Indium Film Surface

Uniformly distributed indium hillocks are grown on silicon substrates by dc magnetron sputtering. The morphologies and the microstructures have been investigated by scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and x-ray diffraction （XRD）. From the TEM and SEM images, we find that, at the earlier stage, the grain coalescent process dominates. This coalescent process induces a larger compressive stress. We believe that the drive force for hillock growth comes from this compressive stress. Under this compressive stress, the grain locating in the middle of several grains are extruded from these grains, and then a hillock forms with the increasing deposition time. For low melting point and high diffusion coefficient metal, such as bismuth and indium, this spontaneous-hillock growth mechanism can be used to fabricate well aligned nanostructures.

Al-induced Lateral Crystallization of Amorphous Si Thin Films by Microwave Annealing

Al-induced lateral crystallization of amorphous silicon thin films by microwave annealing is investigated.The crystallized Si films are examined by optical microscopy,Raman spectroscopy,transmission electron microscopy and transmission electron diffraction micrography.After microwave annealing at 480 ℃ for 50 min,the amorphous Si is completely crystallized with large grains of main (111) orientation.The rate of lateral crystallization is 0.04μm/min.This process,labeled MILC-MA,not only lowers the temperature but also reduces the time of crystallization.The crystallization mechanism during microwave annealing and the electrical properties of polycrystalline Si thin films are analyzed. This MILC-MA process has potential applications in large area electronics.

Fabrication of 2D ZnO Nanosheet Thin Film by a Simple Two-Step Approach

In this paper,2D single-crystalline ZnO nanosheets thin film was fabricated successfully on silicon wafer by a simple two-step approach.XRD,SEM and TEM were used to characterize the phase structures and morphologies of ZnO nanosheets film.