Ca Silicide Films on Si(1 0 0) and Si(1 1 1) Substrates: Structure, Optical and Electrical Properties

The crystal structure, optical and electrical properties of Ca silicide films grown by MBE and RDE processes on Si(1 0 0) and Si(1 1 1) substrates have been compared. Optical spectroscopy studies, including Raman spectroscopy, have shown two silicide phases: CaSi2 and CaSi. The RDE-grown film on Si(1 1 1) substrate with the CaSi2 phase is characterized by higher transparency than MBE-grown films. Therefore, the CaSi2 RDE-grown phase is found to be predominant and has a lower absorption in the IR region of the spectrum. After 1.5-year storage of Ca silicide film oxidation, partial destruction of the CaSi2 phase and conservation of the CaSi layer were revealed by TEM and HRTEM analyses. The complex behavior of magnetoresistance versus magnetic induction, including positive and negative curves, has been found for the MBE-grown films in the temperature range of 1.3–300[Formula: see text]K. The RDE-grown CaSi2 film has displayed a semiconducting type of the magnetoresistance.

Effect of annealing temperature and laser pulse energy on the optical properties of CuO films prepared by pulsed laser deposition

In this work; copper oxide films (CuO) were fabricated by PLD. The films were analyzed by UV-VIS absorption spectra and their thickness by using profilometer. Pulsed Nd:YAG laser was used for prepared CuO thin films under O2 gas environment with varying both pulse energy and annealing temperature. The optical properties of as-grown film such as optical transmittance spectrum, refractive index and energy gap has been measured experimentally and the effects of laser pulse energy and annealing temperature on it were studied. An inverse relationship between energy gap and both annealing temperature and pulse energy was observed.

Rectifying characteristics and tunable magnetoresistance in heterojunctions of La0.9Hf0.1MnO3/0.05 wt.% Nb-doped SrTiO3

La[Formula: see text]Hf[Formula: see text]MnO3 films were grown on 0.05 wt.% Nb-doped SrTiO3 substrates by pulsed laser deposition. X-ray diffraction measurements demonstrated that our samples were of good epitaxy and single-crystal. The temperature-dependent resistance has been investigated. It was observed that the as-grown film of La[Formula: see text]Hf[Formula: see text]MnO3 exhibited a typical paramagnetic-ferromagnetic transition. Heterojunctions of La[Formula: see text]Hf[Formula: see text]MnO3/0.05 wt.% Nb-doped SrTiO3 exhibited-asymmetric current–voltage characteristics and a remarkable temperature-dependent rectifying behavior in a wide temperature range (from 40 K to 300 K). And the most remarkable observation of this work is the existence of a crossover from positive to negative magnetoresistance in the La[Formula: see text]Hf[Formula: see text]MnO3/0.05 wt.% Nb-doped SrTiO3 heterojunction as the temperature decreases. A temperature-dependent magnetoresistance was studied as well. The rectifying characteristics and tunable magnetoresistance of these heterojunctions may be attributed to band structure of La[Formula: see text]Hf[Formula: see text]MnO3/0.05 wt.% Nb-doped SrTiO3 heterojunction.

INFLUENCE OF ANNEALING TREATMENT ON THE PHYSICAL PROPERTIES OF InAlN FILMS

In this work, pure indium and aluminum targets were co-sputtered in a reactive argon–nitrogen environment at 200°C to deposit InAlN film on the GaAs substrate in the presence of a ZnO buffer layer. The as-grown film was annealed at 750°C for 1 h in a high temperature furnace under nitrogen ambient. XRD pattern of the as-grown film did not display any diffraction peak relating to the InAlN due to its poor structural crystallinity, however, the annealed film exhibited InAlN diffraction peaks corresponding to (002), (101) and (102) planes. A significant increase in the grain size and the surface roughness was observed after the films' annealing. Raman spectroscopy revealed A1 (LO) and E2 (high) phonon modes whereas the PL analysis showed a luminescence peak at 2 eV in the annealed film. The Hall measurements indicated an increase in the carrier concentration and electron mobility after the annealing which was accompanied by a decrease in electrical resistivity of the film. The dark current–voltage (I–V) characteristics of the as-grown and the annealed films were also recorded to investigate the barrier height and the ideality factor.

Effect of Growth Pressure on Structural Properties of SiC Film Grown on Insulator by Utilizing Graphene as a Buffer Layer

Heteroepitaxial growth of silicon carbide (SiC) on graphene/SiO₂/Si substrates was carried out using a home-made hot-mesh chemical vapor deposition (HM-CVD) apparatus. Monomethylsilane (MMS) was used as single source gas while hydrogen (H₂) as carrier gas. The substrate temperature, tungsten mesh temperature, H₂ flow rate and distance between mesh and substrate were fixed at 750 °C, 1700 °C, 100 sccm and 30 mm, respectively. The growth pressures were set to 1.2, 1.8 and 2.4 Torr. The growth of 3C-SiC (111) on graphene/SiO₂/Si were confirmed by the observation of θ-2θ diffraction peak at 35.68°. The diffraction peak of thin film on graphene/SiO₂/Si substrate at pressure growth is 1.8 Torr is relatively more intense and sharper than thin film grown at pressure growth 1.2 and 2.4 Torr, thus indicates that the quality of grown film at 1.8 Torr is better. The sharp and strong peak at 33° was observed on the all film grown, that peak was attributed Si(200) nanocrystal. The reason why Si (200) nanocrystal layer is formed is not understood. In principle, it can’t be denied that the low quality of the grown thin film is influenced by the capability of our home-made apparatus. However, we believe that the quality can be further increased by the improvement of apparatus design. As a conclusion, the growth pressures around 1.8 Torr seems to be the best pressures for the growth of heteroepitaxial 3C-SiC thin film.

Novel chemical route for atomic layer deposition of MoS2 thin film on SiO2/Si substrate

An amorphous MoS2 thin film is grown at 100 °C on SiO2/Si by atomic layer deposition using molybdenum hexacarbonyl and dimethyldisulfide. The as-grown film is crystallized with (002) basal planes in a direction parallel to the substrate.

Structural and Optical Properties of In0.27Ga0.73N/Si (111) Film Grown Using PA-MBE Technique

In this paper, InGaN/GaN/AlN/Si (111) structure was grown using a plasma-assisted molecular beam epitaxy (PA-MBE) technique. The structural and optical properties of grown film have been characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), high resolution X-ray diffraction (HR-XRD) and photoluminescence (PL). Indium-mole fraction has been computed to be 0.27 using XRD data and Vegards law with high grain size and low tensile strain. Room-temperature photoluminescence revealed an intense peak at 534 nm (2.3 eV) related to our sample In0.27Ga0.73N.

Surface Corrugation and Stacking Misorientation in Multilayers of Graphene on Nickel

Graphene films were grown on thin polycrystalline Ni using a buried amorphous carbon (a-C) layer as C source. Rapid thermal processes (RTP) at temperatures from 600 to 800°C were used to promote C diffusion into Ni and its subsequent segregation on Ni surface, during the sample cool down. RTP at 800°C was the optimal condition for graphene film formation. Micro-Raman spectroscopy showed that the grown film is mostly composed by multilayers of graphene. Atomic force microscopy showed that the film presents peculiar corrugations (wrinkles), isotropically oriented and with heights ranging from from ~1 to ~15 nm. Selected area diffraction by transmission electron microscopy on the MLG membranes shows a rotational disorder between the stacked graphene layers.

Epitaxy of Porous and Photocatalytically Active TiO2 Films at 50°C

Epitaxial anatase TiO2 thin films were grown on (001) oriented SrTiO3 single crystal substrates by liquid phase deposition at 50°C. The film consisted of nanosized crystallites and exhibited a significant void fraction of 31 %. This contributed to the cracking of thicker films due to the generation of capillary stresses in the nanosized pores during drying. This porosity also comes in useful during the photodegradation of a methylene blue dye by an as-grown film.