二維半導(dǎo)體器件電子輸運(yùn)性質(zhì)研究
發(fā)布時(shí)間：2018-08-21 13:05
【摘要】：自2004年石墨烯被發(fā)現(xiàn)以來,由于其極為獨(dú)特的電子與光電子特性,二維材料在未來器件中的應(yīng)用得到了學(xué)術(shù)界廣泛關(guān)注。過渡金屬硫化物(TMDC)是石墨烯之外最受關(guān)注的一類二維材料,其強(qiáng)的面內(nèi)共價(jià)鍵以及比較弱的層間相互作用使其極易通過剝離的方法得到單層樣品。盡管TMDC的研究已有幾十年的歷史,近年來對低維材料的表征以及器件加工工藝的發(fā)展,其在器件應(yīng)用領(lǐng)域有了很多新的發(fā)展機(jī)會。二硫化鉬(MoS2)和二硫化鎢(WS2)是典型的寬禁帶(單層樣品禁帶寬度分別為1.8eV和2.0 eV)二維半導(dǎo)體型TMDC,在器件應(yīng)用上,具備低靜態(tài)能耗,高開關(guān)比,高遷移的優(yōu)良性能,二維的晶體結(jié)構(gòu)可以有效一直隨器件尺寸降低帶來的短溝道效應(yīng),同時(shí)其器件加工工藝與傳統(tǒng)硅基材料保證高度兼容性,被視為后硅時(shí)代集成電路極具潛力的材料。遷移率一直被視為判斷器件性能的重要指標(biāo)之一,通過理論計(jì)算,單層MoS2室溫聲子極限遷移率可達(dá)到410cm2/Vs,而WS2理論電子遷移率則超過1000cm2/Vs,而在此之前實(shí)驗(yàn)得到的最高遷移率僅為40～50cm2/Vs,遠(yuǎn)遠(yuǎn)低于其理論值；研究組前期工作中在對材料進(jìn)行表征時(shí)發(fā)現(xiàn)天然MoS2存在大量的原子缺陷,缺陷嚴(yán)重制約了器件性能的提高；同時(shí)對于材料輸運(yùn)機(jī)制的研究也沒能完全解釋實(shí)驗(yàn)上所觀察到的現(xiàn)象,比如金屬到絕緣體轉(zhuǎn)變(MIT, Metal to insulating transition),基于以上分析,我們開展了一系列關(guān)于MoS2和WS2缺陷修復(fù)的背柵極場效應(yīng)晶體管電子輸運(yùn)的研究,主要研究內(nèi)容如下：(1)采用硫醇化學(xué)方法對MoS2表面的S原子缺陷進(jìn)行修復(fù),通過對比前后高分辨透射電子顯微鏡(HR-TEM, High resolution transmission electron microscopy)圖片統(tǒng)計(jì)分析發(fā)現(xiàn)硫醇可以有效修復(fù)MoS2表面的S空位缺陷。我們分別對未處理-單面修復(fù)-雙面修復(fù)的三種MoS2樣品制備了背柵器件,研究缺陷修復(fù)對電子輸運(yùn)的影響。雙面修復(fù)樣品室溫遷移率達(dá)到80Vs,為目前報(bào)道的最高記錄。通過對三種不同器件的變溫輸運(yùn)數(shù)據(jù)進(jìn)行擬合分析,發(fā)現(xiàn)MoS2輸運(yùn)中MIT現(xiàn)象主要是缺陷引入的局域態(tài)所導(dǎo)致的。通過進(jìn)一步的理論分析,我們搭建了一套完整的理論模型,考慮了樣品內(nèi)存在的多種散射機(jī)制(聲子,帶電雜質(zhì),短程散射)以及局域態(tài)對電子的束縛,該模型可以定量的計(jì)算分析器件遷移率,電導(dǎo)率隨溫度的變化趨勢,并可以給出MIT的微觀物理意義。(2)通過原子層沉積技術(shù)(ALD, Atomic Layer Deposition)在氧化硅表面沉積～10nm高介電常數(shù)的Al203,我們在沉積的高K值的氧化物表面制備WS2器件,發(fā)現(xiàn)相比氧化硅表面,局域化電子明顯減少,器件在高載流子濃度時(shí)表現(xiàn)出明顯的金屬性傳輸。室溫下,器件遷移率相比氧化硅表面提高100%,低溫下遷移率達(dá)到氧化硅襯底器件100倍以上。通過采用和MoS2相似的理論模型進(jìn)行擬合分析,我們發(fā)現(xiàn)WS2的性能提高主要來自高質(zhì)量的high-κ界面上電子陷阱(trap)濃度的減少。為了進(jìn)一步提高器件性能,我們結(jié)合了硫醇化學(xué)修飾的方法,進(jìn)一步降低器件的trap濃度,得到了室溫和低溫遷移率均明顯高于已有報(bào)道的結(jié)果,為當(dāng)前遷移率記錄。
[Abstract]:Since the discovery of graphene in 2004, due to its unique electronic and optoelectronic properties, the application of two-dimensional materials in future devices has attracted wide attention in academia. Although TMDC has been studied for decades, the characterization of low-dimensional materials and the development of device fabrication technology in recent years have provided many new opportunities for development in device applications. Molybdenum disulfide (MoS2) and tungsten disulfide (WS2) are typical wide band gaps. Two-dimensional (1.8eV and 2.0eV) semiconductor TMDC have the advantages of low static energy consumption, high switching ratio and high mobility in device applications. Two-dimensional (2-D) crystal structure can effectively reduce the short channel effect caused by the decrease of device size. At the same time, its device fabrication process ensures high compatibility with traditional silicon-based materials, which is regarded as the post-silicon era. Mobility has always been regarded as one of the most important parameters to judge the performance of integrated circuits. Theoretical calculations show that the phonon limiting mobility of single-layer MoS2 can reach 410 cm 2/Vs at room temperature, whereas the theoretical electron mobility of WS2 exceeds 1000 cm 2/Vs. The highest mobility of the previous experiments is only 40-50 cm 2/Vs, which is much lower than that of the previous experiments. In the previous work of the research group, a large number of atomic defects were found in natural MoS2, which severely restricted the improvement of device performance. At the same time, the study of material transport mechanism could not fully explain the observed phenomena, such as metal to insulator transition (MIT, Metal to insulati). Based on the above analysis, we have carried out a series of studies on electron transport in MoS2 and WS2 defect-repaired back-gate field effect transistors. The main research contents are as follows: (1) Mercaptan chemical method was used to repair S atom defect on MoS2 surface, and high-resolution transmission electron microscopy (HR-TEM, High res) was compared before and after repair. Statistical analysis of the images shows that mercaptan can effectively repair S-vacancy defects on the surface of MoS2. We fabricated three kinds of MoS2 samples, untreated-unilateral-bilateral, to study the effect of defect repair on electron transport. By fitting and analyzing the temperature-dependent transport data of three different devices, it is found that the MIT phenomenon in MoS2 transport is mainly caused by the local state introduced by the defect. The model can quantitatively calculate and analyze the mobility of the device, the variation of the conductivity with temperature, and give the micro-physical meaning of MIT. (2) Al203 with high dielectric constant of 10 nm was deposited on the surface of silicon oxide by atomic layer deposition (ALD). WS2 devices were fabricated on the deposited oxide surfaces with high K values. The localized electrons were significantly reduced compared with the silicon oxide surfaces, and the devices exhibited significant metal transport at high carrier concentrations. We found that the performance improvement of WS2 was mainly due to the reduction of trap concentration at the High-kappa interface. In order to further improve the device performance, we combined mercaptan chemical modification method to further reduce trap concentration, and obtained room temperature and low temperature transition. The mobility rate was significantly higher than the reported results.
【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TN303
本文編號：2195822
[Abstract]:Since the discovery of graphene in 2004, due to its unique electronic and optoelectronic properties, the application of two-dimensional materials in future devices has attracted wide attention in academia. Although TMDC has been studied for decades, the characterization of low-dimensional materials and the development of device fabrication technology in recent years have provided many new opportunities for development in device applications. Molybdenum disulfide (MoS2) and tungsten disulfide (WS2) are typical wide band gaps. Two-dimensional (1.8eV and 2.0eV) semiconductor TMDC have the advantages of low static energy consumption, high switching ratio and high mobility in device applications. Two-dimensional (2-D) crystal structure can effectively reduce the short channel effect caused by the decrease of device size. At the same time, its device fabrication process ensures high compatibility with traditional silicon-based materials, which is regarded as the post-silicon era. Mobility has always been regarded as one of the most important parameters to judge the performance of integrated circuits. Theoretical calculations show that the phonon limiting mobility of single-layer MoS2 can reach 410 cm 2/Vs at room temperature, whereas the theoretical electron mobility of WS2 exceeds 1000 cm 2/Vs. The highest mobility of the previous experiments is only 40-50 cm 2/Vs, which is much lower than that of the previous experiments. In the previous work of the research group, a large number of atomic defects were found in natural MoS2, which severely restricted the improvement of device performance. At the same time, the study of material transport mechanism could not fully explain the observed phenomena, such as metal to insulator transition (MIT, Metal to insulati). Based on the above analysis, we have carried out a series of studies on electron transport in MoS2 and WS2 defect-repaired back-gate field effect transistors. The main research contents are as follows: (1) Mercaptan chemical method was used to repair S atom defect on MoS2 surface, and high-resolution transmission electron microscopy (HR-TEM, High res) was compared before and after repair. Statistical analysis of the images shows that mercaptan can effectively repair S-vacancy defects on the surface of MoS2. We fabricated three kinds of MoS2 samples, untreated-unilateral-bilateral, to study the effect of defect repair on electron transport. By fitting and analyzing the temperature-dependent transport data of three different devices, it is found that the MIT phenomenon in MoS2 transport is mainly caused by the local state introduced by the defect. The model can quantitatively calculate and analyze the mobility of the device, the variation of the conductivity with temperature, and give the micro-physical meaning of MIT. (2) Al203 with high dielectric constant of 10 nm was deposited on the surface of silicon oxide by atomic layer deposition (ALD). WS2 devices were fabricated on the deposited oxide surfaces with high K values. The localized electrons were significantly reduced compared with the silicon oxide surfaces, and the devices exhibited significant metal transport at high carrier concentrations. We found that the performance improvement of WS2 was mainly due to the reduction of trap concentration at the High-kappa interface. In order to further improve the device performance, we combined mercaptan chemical modification method to further reduce trap concentration, and obtained room temperature and low temperature transition. The mobility rate was significantly higher than the reported results.
【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TN303
【共引文獻(xiàn)】
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1 胡偉;碳納米材料的第一性原理研究[D];中國科學(xué)技術(shù)大學(xué);2013年
2 郭穎;適用于極端與惡劣環(huán)境中的掃描隧道顯微鏡的研制[D];中國科學(xué)技術(shù)大學(xué);2014年
3 司晨;石墨烯及其衍生物：摻雜、應(yīng)變與界面效應(yīng)的理論研究[D];清華大學(xué);2014年
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5 陶瑩;石墨烯基新型多孔碳納米材料的可控構(gòu)建及性質(zhì)研究[D];天津大學(xué);2014年
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1 李晶;碳基半導(dǎo)體器件的高頻特性[D];溫州大學(xué);2013年
2 張娜;碳雜化磁性納米材料的理論設(shè)計(jì)與性能調(diào)控[D];中國科學(xué)技術(shù)大學(xué);2014年
3 韓碭;石墨烯化學(xué)氣相淀積生長、表征及機(jī)理研究[D];西安電子科技大學(xué);2014年
4 晏子來;基于石墨烯與硫化鉬層狀材料的理論計(jì)算及實(shí)驗(yàn)制備[D];中南大學(xué);2014年
5 李寶龍;基于分子結(jié)構(gòu)力學(xué)模型的石墨烯彈性屈曲研究[D];天津大學(xué);2014年
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