Электронно-стимулированная десорбция атомов лития из слоев лития на поверхности Li-=SUB=-x-=/SUB=-Au-=SUB=-y-=/SUB=-

For the first time, semiconductor 2D layers LixAuy have been created on the surface of gold deposited on a tungsten substrate. The processes of electron-stimulated desorption (ESD) of Li atoms in the Li / LixAuy / Au / W system are studied. It is shown that ESD processes occur in the Li monolayer and the LixAuy layer closest to it. A model of ESD of Li atoms in the Li / LixAuy / Au / W system is proposed.

Десорбция атомов калия, стимулированная электронным облучением системы K/K-=SUB=-x-=/SUB=-Au-=SUB=-y-=/SUB=-

Electron-stimulated desorption of K atoms from the surface of potassium atoms on KxAuy was discovered. A KxAuy layer on a tungsten substrate with a gold film deposited on it with a thickness of not more than 5 atomic layers of gold. A quasi-resonant dependence on the energy of the exciting electrons of the electron-stimulated desorption was found. The quasi-resonance dependence is due to the excitation of core levels of Au 5p3/2 and Au 5p1/2. A model of electron-stimulated desorption of K atoms in the K/KxAuy system is proposed that adequately describes the processes that occur during electron-stimulated desorption of potassium atoms. The processes of electron-stimulated desorption excitation of potassium atoms occur at the K/KxAuy interface.

Nucleation Control in Physical Vapor Transport Growth of AlN Single Crystals on Polycrystal Tungsten Substrates

The improved resistively-heated furnace with two heaters established a vertical thermal gradient to control nucleation during AlN single crystals Physical Vapor Transport (PVT) growth on polycrystal tungsten substrates. During the high temperature (> 1850 °C) heating process, the reverse temperature field (i.e., the temperature difference between the sublimation zone and the crystalline zone ΔT < 0) was obtained to reduce the number of nuclei on the tungsten substrate. During growth, the proper positive values of ΔT T were chosen to content the supersaturation values (0.25 < S < 0.3). The reverse temperature condition during high temperature (> 1850 °C) cooling was fulfilled to avoid recrystallization on grown AlN crystal. AlN single crystals made through the method were characterized by X-ray diffractions (XRD) and Raman spectroscopy.

Comparative Study of the Reactivity of the Tungsten Oxides WO2 and WO3 with Beryllium at Temperatures up to 1273 K

Tungsten oxides play a pivotal role in a variety of modern technologies, e.g., switchable glasses, wastewater treatment, and modern gas sensors. Metallic tungsten is used as armor material, for example in gas turbines as well as future fusion power devices. In the first case, oxides are desired as functional materials; while in the second case, oxides can lead to catastrophic failures, so avoiding the oxidation of tungsten is desired. In both cases, it is crucial to understand the reactivity of tungsten oxides with other chemicals. In this study, the different reactivities of tungsten oxides with the highly-oxophilic beryllium are studied and compared. Tungsten-(IV)-oxide and tungsten-(VI)-oxide layers are prepared on a tungsten substrate. In the next step, a thin film of beryllium is evaporated on the samples. In consecutive steps, the sample is heated in steps of 100 K from room temperature (r. t.) to 1273 K. The chemical composition is investigated after each experimental step by high-resolution X-ray photoelectron spectroscopy (XPS) for all involved core levels as well as the valence band. A model is developed to analyze the chemical reactions after each step. In this study, we find that tungsten trioxide was already reduced by beryllium at r. t. and started to react to form the ternary compounds BeWO3 and BeWO4 at temperatures starting from 673 K. However, tungsten dioxide is resistant to reduction at temperatures of up to 1173 K. In conclusion, we find WO2 to be much more chemically resistant to the reduction agent Be than WO3.