Various materials have been examined to use for electron emitters. This paper reviews the results with regard to the materials for several practical electron emitters such as oxide cathodes, impregnated cathodes, LaB6 and semiconductors with negative electron affinity surface. Operation mechanisms, surface structures and stabilities are also described.
The scanning tunneling microscope (STM) provide a sophisticated surface topographic imaging and analysis method in various environments. It has been well demonstrated that imaging graphite surfaces is possible with atomic resolution in air as well as in ultra-high vacuum. However, recent application of STM for samples immersed in aqueous solutions have suggested that STM might become a powerful tool for in-situ electrode surface characterization in the field of electrochemistry. Recent advances in STM in liquid systems are described in this article.
Sucface levels and surface properties such as adsorptive and catalytic abilities of alkaline earth metal oxides strongly depend on coordinative unsaturation of intrinsic surface ions. Both theoretical and experimental works reveal the formation of two surface levels due to MgLC2+ and OLC2-, respectively, where LC denotes low coordination, within the bulk band gap. The surface levels originating from OLC2- go up with lowering of its coordination number and act as electron donative and basic centers. In many cases adsorptions and catalytic reactions proceed on dual active sites of MgLC2+-OLC2- types which can heterolytically dissociate molecules. Another type of adsorption is also possible on the OLC2- site which donates its electron to adsorbed molecules with high electron affinity. Cooperative role of MgLC2+ is also necessary in this case. Coordination numbers have been tentatively assigned to these active sites.
The interface characteristics of Au-deposited CdHgTe and ZnHgTe crystals have been investigated by means of AES, XPS and ELS. Electron beam-heating effect in AES spectroscopy measurements is found to be significant for both Hg desorption and the migration of the constituents of these compounds. During the deposition of nonreactive Au metal at room temperature, indiffusion of Au and outdiffusion of Te were observed. An interdiffusion model is tentatively proposed in which Te atoms diffuse via grain boundary of metal films and Au atoms may diffuse via Zn lattice sites.
We tried to obtain the nearest-neighbour spacing of a titanium thin film and an amorphous TiFe alloy film using EAPFS method. In the case of the titanium thin film, the values obtained on the basis of Ti-L1 peak show 2.93±0.08Å for l=0, 1 and 2.58±0.08Å for l=2. Whereas, the values obtained on the basis of Ti-L2, 3 peak show 3.19±0.05Å for l=0, 1 and 2.87±0.05Å for l=2, respectively. If we assume that the excitation to l=0, 1 is prominent for Ti-L1 peak and to l=2 for Ti-L2, 3 peak, these values are in good agreement with the bulk ones (2.91Å). By using the same procedure to fine structure of amorphous TiFe alloy film, we can obtain the nearest-neighbor 2.58±0.06Å and 2.44±0.06Å for Ti-L1 peak and 2.57±0.05Å for Ti-L2, 3 peak, respectively.
It has been experimentally demonstrated that the injection of 2.45GHz microwave power into an evacuated vacuum vessel promotes outgassing from the wall. The mechanisms of the interaction between gas-adsorbed surface and microwave are discussed from the experimental results on outgassing characteristics. The increment of gas desorption rate by microwave injection is considered to be due to the dielectric heating of adsorbed H2O molecules having a permanent dipole moment, surface heating by an induced current in the surface skin depth, and micro-discharges which occured near the wall surface.
The general principle, functions, and problems of Semiconductor photoelectrochemical (PEC) cells related to solar energy conversion have been described. Recent progress in this field has been outlined with regard to the following subjects : (1) the mechanism and control of semiconductor corrosion (decomposition) reactions, (2) the improvement of the efficiency and stability of semiconductor PEC cells by utilizing adsorption of reducing or oxidizing agents in solution, (3) the molecular mechanism of the photooxidation reaction of water at an n-TiO2 electrode, (4) a novel approach to highly efficient PEC cells by use of semiconductor electrodes coated with discontinuous metal layers.
Since 1976 when Carlson and Wronski demonstrated the amorphous silicon (a-Si) solar cell, it has been on a focus of attention as a low cost solar cell. Aided by the accelerative promotion of the Sunshine Project in Japan, the DOE plan in the U.S, and various countries' plans, numerous research breakthroughs have led to rapid improvement in conversion efficiency. Recently, conversion efficiency of more than 11% was achieved for single-junction structures, and furthermore, more than 13% for multi-junction structures. Since the world's first electronic calculator powered by an a-Si solar cell was put on the market in 1980, consumer electronics and stand-alone systems have been continuously growing in number and in types. This paper reports on recent development in a-Si solar cells. Highly efficient fabrication technologies for a-Si solar cells are mentioned, and the present status of the industrialization of a-Si solar cells is described.
Interest in surface acoustic waves has increased year by year since Lord Rayleigh first found their existence. These waves are of modes of propagation of elastic energy along the free surface of an infinite half-space in which the associated energy density is concentrated within a distance of the order of a wavelength below the free surface. Current interest in surface acoustic waves is being intensified by their potentialities in signal-processing devices. This is, partly, because the devices can be made with a concomitant size reduction corrresponding to the ratio of the velocity of the acoustic waves to that of the electromagnetic waves, and because such waves can interact with the adjacent media on the propagation surface. In this review the research trends of the surface acoustic wave devices are described.