Temperature dependence of the bandgap of Eu doped {ZnCdO/ZnO}30 multilayer structures

In situ Eu-doped {ZnCdO/ZnO}30 multilayer systems were grown on p-type Si-substrates and on quartz substrates by plasma-assisted molecular beam epitaxy. Various Eu concentrations in the samples were achieved by controlling temperature of the europium effusion cell. The properties of as-grown and annealed {ZnCdO/ZnO}30:Eu multilayers were investigated using secondary ion mass spectrometry (SIMS) and X-ray diffraction methods. SIMS measurements showed that annealing at 700{\deg}C and 900{\deg}C practically did not change the Eu concentration and the rare earth depth profiles are uniform. It was found that the band gap depends on the concentration of Eu and it was changed by rapid thermal annealing. Varshni and Bose-Einstein equations were used to describe the temperature dependence of the band gap of {ZnCdO/ZnO}30:Eu multilayer structures and Debye and Einstein temperatures were obtained.Comment: 16 pages, 8 figures, 3 table

Effect of rapid thermal annealing on short period {CdO/ZnO}m SLs grown on m-Al2O3

Here, we report on the characterization of {CdO/ZnO}m superlattice structures (SLs) grown by plasma assisted molecular beam epitaxy. The properties of as-grown and annealed SLs deposited on m-oriented sapphire were investigated by secondary ion mass spectrometry (SIMS) and scanning electron microscopy (SEM) in cathodoluminescence (CL) and energy dispersive X-ray modes. The deformation of the crystallographic structure of SLs was observed after rapid thermal annealing at 900{\deg}C in oxygen flow due to migration and segregation of Cd atoms. SIMS measurements revealed that the distributions of cadmium in the annealed samples depend on the thicknesses of the CdO and ZnO sublayers in the as grown superlattice structures. Depth-resolved CL measurements showed that shifting of the near band edge emission peaks is closely related to the Cd profiles measured with SIMS.Comment: 14 pages, 6 figure

Structural Properties of MnTe, ZnTe, and ZnMnTe

Structural properties of ZnTe, MnTe, and Mn 1−x Zn x Te alloy with zinc--blende, NiAs, and wurtzite phases were investigated by ab initio calculations. The calculated structural properties are in good agreement with the available experimental data. Theory predicts that the zinc-blende phase is more stable than wurtzite for all compositions. Mn1−xZnxTe samples with 0.01 < x < 0.20 were grown by MBE. X-ray analysis of their crystalline structure revealed the presence of zinc-blende, wurtzite, and NiAs phases. The dominant phase changes from NiAs for the sample with x = 0.01 to wurtzite for x = 0.20. The observed stabilization of the wurtzite phase is possibly due to the hexagonal structure of the MnTe buffer

Structural Properties of MnTe, ZnTe, and ZnMnTe

Structural properties of ZnTe, MnTe, and Mn$\text{}_{1-x}$Zn$\text{}_{x}$Te alloy with zinc-blende, NiAs, and wurtzite phases were investigated by ab initio calculations. The calculated structural properties are in good agreement with the available experimental data. Theory predicts that the zinc-blende phase is more stable than wurtzite for all compositions. Mn$\text{}_{1-x}$Zn$\text{}_{x}$Te samples with 0.01 < x < 0.20 were grown by MBE. X-ray analysis of their crystalline structure revealed the presence of zinc-blende, wurtzite, and NiAs phases. The dominant phase changes from NiAs for the sample with x=0.01 to wurtzite for x=0.20. The observed stabilization of the wurtzite phase is possibly due to the hexagonal structure of the MnTe buffer

Structural Properties of MnTe, ZnTe, and ZnMnTe

Structural properties of ZnTe, MnTe, and Mn$\text{}_{1-x}$Zn$\text{}_{x}$Te alloy with zinc-blende, NiAs, and wurtzite phases were investigated by ab initio calculations. The calculated structural properties are in good agreement with the available experimental data. Theory predicts that the zinc-blende phase is more stable than wurtzite for all compositions. Mn$\text{}_{1-x}$Zn$\text{}_{x}$Te samples with 0.01 < x < 0.20 were grown by MBE. X-ray analysis of their crystalline structure revealed the presence of zinc-blende, wurtzite, and NiAs phases. The dominant phase changes from NiAs for the sample with x=0.01 to wurtzite for x=0.20. The observed stabilization of the wurtzite phase is possibly due to the hexagonal structure of the MnTe buffer

Characterization of ZnO Films Grown at Low Temperature

ZnO thin films were grown by atomic layer deposition method at extremely low temperature using a reactive diethylzinc as a zinc precursor. Optical properties, electrical properties and surface morphology were examined by photoluminescence, Hall effect and atomic force microscope. The study shows correlation between optical, electrical properties and surface morphology in a series of samples of different thickness

ZnO by ALD - Advantages of the Material Grown at Low Temperature

The 3D-architecture is a prospective way in miniaturization of electronic devices. However, this approach can be realized only if metal paths are placed not only at the top, but also beneath the electronic parts, which imposes drastic temperature limitations for the electronic device processing. Therefore last years a lot of investigations are focused on materials which can be grown at low temperature with electrical parameters appropriate for electronic applications. Zinc oxide grown by the atomic layer deposition method is one of the materials of choice. We obtained ZnO-ALD films at growth temperature range between 100°C and 200°C, and with controllable electrical parameters. Free carrier concentration was found to scale with deposition temperature, so it is possible to grow ZnO films with desired conductivity without any intentional doping. We used correlation of electrical and optical parameters to optimize the deposition process. Zinc oxide layers obtained in that way have free carrier concentration as low as $10^{16} cm^{-3}$ and high mobility ($10-50 cm^{2}$/(Vs)), which satisfies requirements for a material used in three-dimensional memories

Photoluminescence Properties of ZnO Nanowires Grown on Ni Substrate

Photoluminescence studies of zinc oxide nanowires produced by a carbo-thermal method on a nickel foil substrate are reported. Two types of as-grown samples: the first - containing only buffer film, and the second - containing both zinc oxide nanowires and buffer film grown in the same technological process, were investigated by means of the temperature-dependent photoluminescence. X-ray diffraction measurements of buffer film show that it is polycrystalline and is composed from wurtzite-type ZnO (main phase) and includes minority phases: rock salt type (Ni,Zn)O and hexagonal C₃N₄. The shape of the apparently monocrystalline nanowires is characterized by hexagonal section matching with the expectations of the hexagonal ZnO structure. The presence of LO-phonon replicas in photoluminescence spectra for the second sample is used as an argument for confirmation that ZnO nanowires are single crystalline. The method of growth of ZnO nanowires on nickel oxide opens perspectives to produce $Zn_{1-x}Ni_{x}O$ diluted magnetic semiconductor nanowires

Epitaxial ZnO Films Grown at Low Temperature for Novel Electronic Application

Monocrystalline films of zinc oxide were grown at 300C by atomic layer deposition. ZnO layers were grown on various substrates like ZnO bulk crystal, GaN, SiC and $Al_2O_3$. Electrical properties of the films depend on structural quality. Structural quality, surface morphology and optical properties of ZnO films were characterized using X-ray diffraction, scanning electron microscopy, and photoluminescence, respectively. High resolution X-ray diffraction spectra show that the rocking curve FWHM of the symmetrical 00.2 reflection equals to 0.058° and 0.009° for ZnO deposited on a gallium nitride template and a zinc oxide substrate, respectively. In low temperature photoluminescence sharp excitonic lines in the band-edge region with a FWHM equal to 4 meV, 5 meV and 6 meV, for zinc oxide deposited on gallium nitride, zinc oxide and sapphire substrate, respectively