【正文】 n of nonequilibrium carriers. According to GaN photocathode NEA property during activation process and after being fully activated, the surface model [GaN(Mg):Cs]: OCs for NEA GaN photocathode after Cs/O activation was given. The depuration method for GaN photocathode was studied by using NEA photocathode activation system and XPS surface analysis system. The chemical cleaning and the heating depuration method were given in detail. After the effective chemical cleaning and the heating of 700℃ about 20 minutes in ultrahigh vacuum system, the oxides and carbon impurities on cathode surface can be effectively removed, and the ideal atom clean surface can be obtained.The photocurrent curves of Cs and Cs/O activation for reflectionmode GaN photocathode were tested by using dedicated experimental system for activating and evaluating of NEA photocathode. Aiming at the formation cause of NEA property for GaN photocathode and according to the rule of photocurrent change during activation period and the surface model of a fully activated photocathode, the activation mechanism of NEA GaN photocathode was studied. The relation of the rule of photocurrent change during activation period and the change of electron affinity during activation period was gotten. The experiment results show: the obvious NEA property can be achieved for GaN photocathode mainly by activating with Cs. The increase extent of photocurrent is not large after introducing O during Cs/O activation process for GaN photocathode. The NEA property formation reasons of GaN photocathode after being fully activated successfully can be well explained using the double dipole layer model [GaN(Mg):Cs]: OCs.The spectral response of fully activated reflectionmode NEA GaN photocathode was measured by using dedicated ultraviolet spectral response measurement instrument. The quantum efficiency curves of reflectionmode NEA GaN photocathode were given in the band region from 230nm to 400nm. The quantum efficiency of reflectionmode NEA GaN photocathode reaches up to % at 230nm, a sharp cutoff characteristic with over two orders of magnitude degradation from 230nm to 400nm has been observed. Based on the former research results, the factors influencing quantum efficiency were also prehensively analyzed. The relation of quantum efficiency and incidence light wavelength, cathode material characteristic and cathode preparation technique was gotten.According to the photocurrent curves and the quantum efficiency curves of fully activated reflectionmode NEA GaN photocathode, aiming at the decay tendency for reflectionmode NEA GaN photocathode and the different decay speeds of quantum efficiency corresponding to the different wave bands, the quantum efficiency decay mechanism of reflectionmode NEA GaN photocathode was studied. The relation of the quantum efficiency decay of reflectionmode NEA GaN photocathode and the reduction of effective dipole quantity was gotten, and the relation of the decay characteristic of quantum efficiency curves and the change of surface barrier shape was also gotten. The surface model [GaN (Mg):Cs]:OCs for GaN photocathode after being activated with cesium and oxygen was used, and the change of energy band and surface barrier in the decay course of quantum efficiency was considered. The conclusions show: the reduction of effective dipole quantity is the basic reason causing quantum efficiency to reduce, and it is the change of surface I, II barrier shape that causes the difference of dropping speeds of quantum efficiency corresponding to different wave bands.Keywords: reflectionmode, NEA, GaN, photocathode, quantum efficiency, surface model, activation, spectral response, stability目 錄摘 要 IAbstract III1 緒論 1 NEA GaN光電陰極概述 1 1 NEA光電陰極的發(fā)現(xiàn) 1 NEA GaN光電陰極的提出 2 NEA GaN光電陰極的研究現(xiàn)狀 4 GaN晶體的生長(zhǎng)技術(shù)現(xiàn)狀 4 GaN基固體探測(cè)器件的研究現(xiàn)狀 5 GaN基真空探測(cè)器件的研究現(xiàn)狀 6 NEA GaN光電陰極的應(yīng)用 9 在紫外探測(cè)領(lǐng)域的應(yīng)用 10 在真空電子源中的應(yīng)用 12 本文研究的背景和意義 14 本文研究的背景 14 本文研究的意義 14 本文研究的主要工作 152 NEA GaN光電陰極光電發(fā)射理論研究 17 GaN晶體概述 17 GaN的晶格結(jié)構(gòu)和主要參數(shù) 17 GaN晶體的特性及能帶結(jié)構(gòu) 18 GaN晶體的本征載流子濃度 20 NEA GaN光電陰極的光電發(fā)射機(jī)理概述 21 NEA GaN光電陰極的結(jié)構(gòu)以及工作模式 24 NEA GaN光電陰極光電發(fā)射過(guò)程 25 25 26 28 GaN光電陰極的量子效率表達(dá)式 31 NEA GaN光電陰極表面模型 33 GaAs光電陰極表面模型的回顧 33 GaN光電陰極表面模型[GaN(Mg):Cs]: OCs 35 GaN光電陰極表面模型[GaN(Mg):Cs]: OCs的討論 37 本章小結(jié) 383 反射式NEA GaN光電陰極制備技術(shù)研究 39 引言 39 激活評(píng)估實(shí)驗(yàn)系統(tǒng)簡(jiǎn)介 41 42 NEA光電陰極的多信息量在線測(cè)控系統(tǒng) 46 46 NEA GaN光電陰極表面的凈化 47 48 49 激活實(shí)驗(yàn) 51 Cs激活 51 Cs/O激活 53 反射式NEA GaN光電陰極激活機(jī)理 55 55 56 58 本章小結(jié) 594 反射式NEA GaN光電陰極光譜響應(yīng)研究 61 61 62 63 GaN光電陰極光譜響應(yīng) 67 反射式NEA GaN光電陰極光譜響應(yīng)曲線特點(diǎn) 67 光譜響應(yīng)曲線的討論 69 影響反射式NEA GaN光電陰極量子產(chǎn)額的因素 69 735 反射式NEA GaN光電陰極穩(wěn)定性研究 74 引言 74 反射式NEA GaN光電陰極的穩(wěn)定性實(shí)驗(yàn) 75 反射式NEA GaN光電陰極穩(wěn)定性實(shí)驗(yàn)介紹 75 反射式NEA GaN光電陰極穩(wěn)定性實(shí)驗(yàn)討論 76 反射式NEA GaN光電陰極量子效率曲線的衰減 78 量子效率衰減的實(shí)驗(yàn) 78 量子效率曲線的衰減結(jié)果分析與討論 79 反射式NEA GaN光電陰極量子效率曲線的恢復(fù) 81 反射式NEA GaN光電陰極重新進(jìn)Cs激活 81 反射式NEA GaN光電陰極重新進(jìn)Cs激活結(jié)果討論 82 本章小結(jié) 846 結(jié)束語(yǔ) 85 本文工作總結(jié) 85 本文的創(chuàng)新點(diǎn) 87 有待進(jìn)一步探索的問(wèn)題 88致 謝 89參考文獻(xiàn) 90附 錄 1011 緒論 NEA GaN光電陰極概述光照射到特定材料上時(shí)光能會(huì)轉(zhuǎn)換成電能，使材料的電性質(zhì)發(fā)生變化，這種因材料吸收了光子能量而產(chǎn)生的電效應(yīng)被稱為光電效應(yīng)。得到了反射式NEA GaN光電陰極量子效率的衰減現(xiàn)象與有效偶極子數(shù)量減小之間的關(guān)系以及量子效率曲線的衰減特點(diǎn)與表面勢(shì)壘形狀改變之間的關(guān)系。結(jié)合國(guó)外對(duì)GaN光電陰極量子效率的研究結(jié)果，綜合分析了影響量子效率的因素，得到了量子效率與入射光波長(zhǎng)、陰極材料特性以及陰極制備水平之間的關(guān)系。利用自行研制的紫外光譜響應(yīng)測(cè)試儀器，測(cè)試了成功激活的反射式GaN光電陰極的光譜響應(yīng)，給出了230nm～400nm波段內(nèi)反射式NEA GaN光電陰極量子效率曲線。實(shí)驗(yàn)表明：GaN光電陰極在單獨(dú)導(dǎo)入Cs激活時(shí)就可獲得明顯的NEA特性，Cs/O激活時(shí)引入O后光電流的增長(zhǎng)幅度不大。利用自行研制的光電陰極激活評(píng)估實(shí)驗(yàn)系統(tǒng)，給出了反射式GaN光電陰極Cs激活及Cs/O激活的光電流曲線。經(jīng)過(guò)有效化學(xué)清洗后，超高真空中GaN樣品在700186。結(jié)合陰極的激活過(guò)程及充分激活后的NEA特性，給出了NEA GaN光電陰極銫（Cs）氧（O）激活后的表面模型[GaN(Mg):Cs]: OCs?！叭侥Ｐ汀保敿?xì)分析了NEA GaN光電陰極從光電子的激發(fā)、體內(nèi)到表面的輸運(yùn)到穿越表面勢(shì)壘逸出到真空的全過(guò)程，導(dǎo)出了光電子隧穿陰極表面勢(shì)壘的透射系數(shù)。摘 要負(fù)電子親和勢(shì)（NEA）GaN光電陰極具有靈敏度高、暗發(fā)射小、發(fā)射電子能量分布集中等優(yōu)點(diǎn)，是非常理想的新型紫外光電陰極。針對(duì)目前NEA GaN光電陰極的基礎(chǔ)理論、制備方法與評(píng)估手段研究的不足，圍繞反射式GaN光電陰極的光電發(fā)射機(jī)理、凈化方法、激活工藝、光譜響應(yīng)測(cè)試以及陰極的穩(wěn)定性能等方面開(kāi)展研究。通過(guò)求解非平衡載流子的擴(kuò)散方程導(dǎo)出了反射式NEA GaN光電陰極的量子效率公式。利用NEA光電陰極激活系統(tǒng)和XPS表面分析系統(tǒng)研究了GaN光電陰極的凈化方法，給出了具體的化學(xué)清洗和加熱凈化工藝。C下加熱20分鐘，可以有效去除陰極表面的氧化物以及C雜質(zhì)，獲得較為理想的原子級(jí)清潔表面。針對(duì)GaN光電陰極NEA特性的成因，結(jié)合激活過(guò)程中光電流變化規(guī)律和成功激活后陰極表面模型，研究了NEA G