Preparation And Characterization Of ZnCdO Films And Lnvestigation Of Al-Os Alloy By First Principles Calculations

In order to realize such optoelectronic devices with high efficiency, a crucial step is the realization of band gap engineering by introducing Cd into ZnO, it can realize the redshift in the luminescence peak of ZnO, and also can used as barrier layers or quantum wells in device heterostructures to Improve efficiency of LEDs by realize the double bind effect for both electron and photon.Presently, this is indeed a problem for ZnCdO alloy with high content of Cd, where crystal quality of the prepared films was very poor internationally. In designing LED or LD structures in ZnO/ZnCdO system, information such as the interface band alignment parameters is no less important than the band gap energies for ZnO. However, there is still a lack of experimental data available. For this reason, we decided to carry out this research, and the details are as follows:(1) Optimization of the growth conduction for ZnCdO film deposited on Al2O3(0001). ZnCdO alloy thin films were prepared on c-plane sapphire (Al2O3(0001)) substrates by Laser-Molecular beam epitaxy (L-MBE). By tuning the substrate temperature, pulse frequency, chamber pressures, etc, we optimized the growth conduction.(2) High-quality Zn1-xCdxO (0≤x<9.93at.%) films on c-plane sapphire (Al2O3(0001)) substrates by L-MBE. The effects of Cd content on the structural and optical properties of Zn1-xCdxO have been investigated, single-phase Zn1-xCdxO thin films with a higher Cd content of9.93at.%have been achieved. The band-gap energy was artificially tuned from3.262to2.949eV.(3) The valence band offset at the ZnO/Zno.9Cd0.1O heterojunction interface has been determined to be0.203eV. Given the band gap difference of0.313eV, the conduction band offset (CBO) is then deduced to be0.110eV, indicating that a type-I band alignment for ZnO/Zno.9Cd0.1O heterojunction. To apply ZnO/Zn1-xCdxO bilayers in electronic devices, it is important to determine the band alignment accurately based on the VBO and CBO. (4) Structural stability and electronic properties of ZnCdO alloys investigated by first-principles calculation. The stability of RS and w-structures of CdO almost had the same stability, but the zb was not so stable. The band gap E%(x) of ternary Zn1-xCdxO is determined by the equation:Eg(x)=1.0223x2-3.46x+3.36, which is agree well with our experimental results.(5) Structural and electronic properties of Al-Os intermetallic compounds investigated by first-principles calculation. The results of the formation heats indicate that the alloying ability of Al3OS2is much stronger than Al13Os4, Al2Os and AlOs. Besides, the bulk modulus increased linearly from72.2to418GPa with increasing Os concentrations from0%to100%. And most of the Al-Os alloys considered are conductors, while the Al2Os alloy appears the characters of semiconductor with an indirect band gap of0.322eV.