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Lu Yuehui,Wu Xuemei,Liu Xianghuai,Zhuge Lanjian 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.45 No.3
It is problematic that electrons are emitted from the Mo grid of pulsed-controlled grid traveling wave tubes, caused by the contamination of cathode evaporation material, i.e. BaO. Some studies show that a Mo grid coated with carbon can greatly suppress grid electron emission. However, the reason for the electron emission suppression is not completely clear. To understand the mechanism of electron emission suppression of a BaO/C/Mo system, carbon lms were prepared on Mo substrates at room temperature by means of DIBSD (dual ion beam sputtering deposition), and BaO layers were coated by using a chemical method. Post-annealing was conducted under a owing nitrogen ambient at 700 C for 1.5 hours. The structure of the as-deposited carbon lms was evaluated by TEM, AES and Raman spectroscopy. The annealed samples, the BaO/ Mo and BaO/C/Mo systems, were analyzed by XPS. The results suggest that the chemical reaction between BaO and C at high temperature eliminates the concentrations of Ba or BaO on the surface of the C/Mo system. It can be believed that the high work function material used as the grid surface coating and elimination of BaO on its surface have a critical eect on grid electron emission suppression. Moreover, the carbon lm was characterized by density, homogeneity and high adhesion, owing to the features of DIBSD.
Liang, Weizheng,Gao, Min,Lu, Chang,Zhang, Zhi,Chan, Cheuk Ho,Zhuge, Lanjian,Dai, Jiyan,Yang, Hao,Chen, Chonglin,Park, Bae Ho,Jia, Quanxi,Lin, Yuan American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.9
<P>Vanadium dioxide (VO<SUB>2</SUB>) is a strong-correlated metal-oxide with a sharp metal-insulator transition (MIT) for a range of applications. However, synthesizing epitaxial VO<SUB>2</SUB> films with desired properties has been a challenge because of the difficulty in controlling the oxygen stoichiometry of VO<SUB><I>x</I></SUB>, where <I>x</I> can be in the range of 1 < <I>x</I> < 2.5 and V has multiple valence states. Herein, a unique moisture-assisted chemical solution approach has been developed to successfully manipulate the oxygen stoichiometry, to significantly broaden the growth window, and to significantly enhance the MIT performance of VO<SUB>2</SUB> films. The obvious broadening of the growth window of stoichiometric VO<SUB>2</SUB> thin films, from 4 to 36 °C, is ascribed to a self-adjusted process for oxygen partial pressure at different temperatures by introducing moisture. A resistance change as large as 4 orders of magnitude has been achieved in VO<SUB>2</SUB> thin films with a sharp transition width of less than 1 °C. The much enhanced MIT properties can be attributed to the higher and more uniform oxygen stoichiometry. This technique is not only scientifically interesting but also technologically important for fabricating wafer-scaled VO<SUB>2</SUB> films with uniform properties for practical device applications.</P> [FIG OMISSION]</BR>