| The electro-optical tensor, current-voltage characteristic,plasmas excited by extreme non-uniform electric field in the atmosphereand Vacuum ultraviolet (VUV) emission of electroluminescent of cubicboron nitride(cBN) single crystals were studied in this thesis.cBN has a zinc blend structure and belongs to the Tdpoint group;thus, it possesses the linear electro-optic effect. Its EO tensorpossesses only three identical non-zero elements, namely,g41=g52=g63.The band gap of cBN is about6.3eV,which is the widest among the III-Vcompounds. Therefore, cBN is transparent in throughout the visible rangeand most of the infrared and ultraviolet spectra; it can also operatein the wide spectral range as the EO material. Furthermore, cBN has avery high laser damage threshold, meaning it can withstand high-powerpulsed or continuous-wave(CW)laser beams. Thus, cBN has potential EOapplications.The determination of the EO coefficients of cBN crystalsis a prerequisite not only for the EO applications, but also for otherstudies(e.g.,for the study of Raman efficiency of cBN and for thepropagation control of the surface wave generated from the interfacebetween the cBN crystal and other isotropic medium.) A transverse EOmodulation system based on these rectangular parallelepiped cBN sampleswhich are obtained by physically cleaving and mechanically grinding andpolishing is built for investigating the linear EO effect and accordingly measuring the experimental value ofg41of cBN crystals.The transverseEO modulation system for measuring the linear EO coefficient of cBN wasbuilt. The light source is a CW semiconductor laser with thewavelength l=650nm. The output beam from the sample is ellipticallypolarized. The intensity of the output beam from the analyzer Ioisdependent on the phase difference Γ, namelyI0=1/2Ii(1+π/Vπ×V)=I1+I2whereIiis the intensity of the input beam, the phasedifference beteween the two eigenpolarization rays induced by themodulating voltage Vm, and Vπis the half-wave voltage relevant to therefractive index, the linear EO coefficient,and the size of the sample.I1and I2can be detected using the Si photodetector connected with thelock-inamplifier.For Vπ=πVmI1/I2, the half-wave voltage Vπcan becalculated. Applying two sample configurations, three identical nonzeroelements of the EO tensor of the cBN crystalg41=g52=g63wereexperimentally measured according to the ratio of the two components (onedepends on the modulating voltage, and the other does not) of the outputbeams. The measured result as3.95pm/V.The measuredg41of the cBNcrystal is much larger than the linear EO coefficients of other III-Vcompounds such as GaAs, GaN, AlN, GaP and so on. So cBN crystals arevery promising EO material. In addition, the measuring method of thelinear EO coefficient adopted in this paper is very convenient andfeasible because it is unnecessary to measure the absolute intensity ofthe probing beam.The current-voltage characteristic of cBN single crystal was studiedon two types electrode structures. One is the parallel plate electrodestructure,the other is needle-plate electrode structure.In the parallelplate electrode structure type, the I-V characteristic can be interpreted by the space charge limited current with traps theory. Inthe needle-plate electrode structure type, the I-V characteristic canbe interpreted by Fowler-Nodheim tunnel effect which needle contactedwith colorless area of cBN single crystal,and the theory of space chargelimited current with sphere-plate elevtrode structure which needle whichneedle contacted with colored area of cBN single crystal.The induced electric field between needle-plate electrodes isextremely non-uniform, and it is the strongest at the needlepoint. Intheory, the infinitesimal curvature radius of the needlepoint will leadto infinite electric field strength. So high dc voltages applied to theneedle-plate electrodes can result in gas ionization from the air gapbetween the electrodes, then the corona discharge will arise and the lowtemperature plasmas will be brought out. In the atmosphere, anunintentionally doped amber cubic boron nitride (cBN) single crystalflake whose sizes are0.3×0.3×0.1mm3was fixed between the tungstenneedle with a diameter of10μm at the needlepoint and the brass plateelectrodes, the two opposite {111} planes of the cBN flake are contactedtightly to the electrodes, that is to say, the cBN flake was substitutedfor the air gap. When the dc voltages, with a range of700-1200V, lowerthan those in the case of air gap, were applied to the needle-plateelectrodes, gas discharge different from the common corona dischargeappeared. It seemed to be glow discharge in the first stage, but transitedinto arc discharge with the increase of the applied voltage, and the lowtemperature plasmas were then induced. When the tungsten needle is chosento be the negative electrode, it was surrounded by the bright blue-violetlight, and the light was expanding from the needlepoint to the end withina distance. While the needle was the positive electrode, the brightblue-violet light was extending along the upper plane of the cBN flake off the needlepoint. The current-controlled differential negativeresistance was synchronously observed. However, no aforementionedphenomena were observed when the cBN flake was substituted by a quartzor mica flake. In the atmosphere, the plasmas excited by extremelynon-uniform electric field using cBN single crystals are not only causedby the air ionization due to the electric field. The initial gas dischargemay be the air ionization induced by the vacuum ultraviolet with awavelength of149nm emitted from the cBN crystal which is excited by theextremely non-uniform electric field, then the extremely non-uniformelectric field keeps the air discharging, and the low temperature plasmasare consequently induced.The vacuum ultraviolet emission from cBN single crystals inextremely non-uniform electric field. In a vacuum chamber, anunintentionally doped amber cBN single crystal was fixed betweenneedle-plate electrodes, and the two opposite {111} planes of the cBNcrystal contacted with the electrodes tightly. When the dc voltageapplied on the cBN crystal reached a critical value between6001550V, the VUV emission from the cBN crystal took place. When the vacuumdegree of the chamber was about3×10-3Pa, the VUV radiation spectrumof the cBN crystal was measured by a VUV spectrometer, the peak wavelengthis about149nm. When the vacuum degree of the chamber was about7×10-4Pa, green PDP phosphors (BaAl12O19:Mn2+) were spread around the junctionbetween the needlepoint and the cBN crystal, and the green fluorescenceexcited by the VUV from cBN could be observed by naked eyes. The VUVemission from the cBN crystal in the extreme non-uniform electric fieldcan be interpreted by the interband and intraband transition and theelectron-hole direct recombination.
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