No abstract

In this paper, high-quality β-Ga2O3 films were grown on silicon substrates by plasma-enhanced atomic layer deposition (PEALD). Effects of annealing temperature on β-Ga2O3 thin films were studied. Atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray reflection (XRR), and ultraviolet (UV) emission spectroscopy were used to systematically characterize Ga2O3 thin films. AFM test results showed that as annealing temperature increased from 500 to 900 °C, the roughness of film increased from 0.542 to 1.58 nm. XPS test results showed that the concentration of oxygen vacancies in annealed films was significantly reduced. After annealing, the energy band of the film increased from 4.73 to 5.01 eV, and the valence band maximum (VBM) increased from 2.58 to 2.67 eV, indicating that the annealing treatment under a nitrogen atmosphere can improve the quality of films. Results demonstrate that high-quality Ga2O3 films can be obtained by the annealing process after atomic layer deposition (ALD). The proposed method can realize an ideal stoichiometric ratio of the Ga2O3 thin film as well as precise control of its optical, electrical, and microstructural properties. This work lays the foundation for future application of Ga2O3 materials in photoelectric detection, power devices, transparent electronics, and other fields.

Since the growth morphology along and perpendicular to the interface is important for supermirror applications, the dependence of this on the reactive gas has been investigated in Ni/Ti multilayers prepared by reactive magnetron sputtering with variable O2/N2 ratios. The interface properties are characterized by GIXRR, XDS, and TEM measurements. Compared to the case without O2, the presence of 20% O2 in the deposition of Ni layers contributes to smooth and abrupt interfaces. It also suppresses the accumulation of interface roughness with the increasing number of layers. However, the abundant oxygen content results in a striking degradation of interface quality associated with the crystallization evolution. Moreover, the lateral correlation length of interfacial roughness exhibits a consistent tendency with the grain size as the oxygen content increases. Following the XPS depth profiles, although N2 and O2 gases were applied in the Ni layer deposition, the N and O were only detected in the Ti layers as the compound for the high chemical activity of Ti. The elemental form in the Ni layers corresponds to the crystalline structure inferred by XRD measurements.

X-rays have developed into an essential tool in variety of fields, such as biology, materials, chemistry, and physics etc. Numerous X-ray types, including the orbital angular momentum (OAM), the Laguerre–Gauss, and the Hermite–Gauss states, have been proposed. This greatly enhances the depth of application of X-ray. The X-ray states described above are mostly produced by binary amplitude diffraction elements. In light of this, this paper proposes a flat X-ray diffraction grating based on caustic theory to generate Airy-type X-ray. It is proved by the simulation of multislice method that the proposed grating can generate the Airy beam in the X-ray field. The results show that the generated beams have a secondary parabolic trajectory deflection with the propagation distance, which is consistent with the theory. Inspired by the success of Airy beam in light-sheet microscope, the Airy-type X-ray can be anticipated to enable novel image capability for bio or nanoscience.