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Preparation And Nature Study Of Photoelectron Materials Based On Porous Silicon

Posted on:2007-11-12Degree:DoctorType:Dissertation
Country:ChinaCandidate:A H PengFull Text:PDF
GTID:1118360182494203Subject:Condensed matter physics
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The research and development of porous silicon have promising applications in photoelectric integrated circuit. Through doping rare earth into porous silicon, the luminescence ranging from ultraviolet, visible to infrared can be obtained, and it can be used in many kinds of photo electricity devices. This thesis mainly described the improvement of porous silicon's preparation technology and enhancement of luminescence intensity for porous silicon by doping rare earth. Rectification character, field emission character of porous silicon and effect of porous silicon on luminescence character of film luminescence material are studied, too. The mainconclusions of the thesis are as follows:(1) Improvement of preparation technology for porous silicon. We studied the effect of changing current and anneal on photoluminescence properties of porous silicon;How does the doping of Fe affect photoluminescence of porous silicon;The photoluminescence of nano-particles of porous silicon in liquid;Through wet etching, we get photoluminescence of porous silicon in different wave range;We find that LaNiO3 electrode whose preparation method is more simple can replace Al electrode.(2) Doping rare earth improves luminescence of porous silicon. Rare earth (Tb, Gd, Pr, Dy, Sc) ions were embedded into porous silicon films by electrochemical method. Fluorescence photo spectrometer and scanning electron microscope were employed to characterize the photoluminescence and surface morphology of samples. The distribution of rare earth ions embedded into porous silicon films was examined by Rutherford backscattering spectrometry. The luminescence intensity of porous silicon after doping Tb is greatly increased. Blue shift of luminescence peak was also observed. The luminescence peaks are attributed to intra-4f transitions of Tb3+, including 5D4 —7F3, 5D4 —7F2 and 5D4 —7F0. Blue luminescence was observed after doping with Gd. When Dy was doped, intense blue light was obtained. The intensity is approximately equal to the red luminescence intensity of the porous silicon without doping. The blue luminescence can be enhanced in a certain extent when proper amounts of Pr and Sc were doped.We find that the blue emission of porous silicon was increased after rare earth was doped. The mechanisms of blue emission may be as follows: new surface states were introduced in porous silicon after rare earth doping and the new bonding O—Si—O—Re—O was formed, so the new emission centers are formed on the surface of porous silicon. The rich energy states of rare ions may play an important role in energy transfer so as to enhance the blue emission intensity.(3) Effect of porous silicon on luminescence properties of films deposited on porous silicon. TiO2: Eu3+ films are deposited on four different substrates: Si, Al, AAO (anodic alumina oxide) and porous silicon. We find that the luminescence intensity on AAO substrate increased 4 times comparing with that on Si or Al, and luminescence intensity decreases obviously on porous silicon substrate. The main reason of decrease is that the surface color of porous silicon is brownish black and the deep color surface absorbs light more and reflects little. The polished Si and Al can reflect light well. We know T1O2: Eu3+ film is transparent, good reflection property of substrate is beneficial to the effective luminescence of the film. Also it is possible that nano silicon in porous silicon absorbs ultraviolet light more than bulk silicon, which weakens the reflection of substrate too. Energy transfer mechanism from TiO2 host to Eu + is deduced through analysis of photoluminescence and photoluminescence excitation spectrum. Concentration quenching of Eu3+ does not appear even at high atomic concentration of 7.69%.(4) Field emission and rectification character of porous silicon. Special porous silicon is prepared which can emit ballistic electrons to examine its field emission character. After electrochemical oxidizing, the character of field emission improved. Cut-in voltage is reduced and emission current is enhanced. Current's diminution in well-proportioned speed in etching one piece of porous silicon, is compared with current keep invariable, we find that the former is an effective method to enhance field emission character. Cut-in voltage is reduced. Emission current increased greatly. As current change, the field emission of samples doesn't show obvious law of change. About rectification character of porous silicon, we get that after electrochemical oxidizing in concentrated sulfuric acid, the rectification character of porous silicondisappear;after annealing in N2, the rectification character of porous silicon increased.
Keywords/Search Tags:porous silicon, rare earth, photoluminescence, field emission, rectification
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