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標題: | 分子束磊晶成長鉍薄膜的電性觀察與分析:半導體態、表面態和反弱局域 Electrical properties observation and analysis of Bismuth thin film grown by MBE: bulk state, surface state and weak antilocalization |
作者: | Chien-Cheng Lu 盧建成 |
指導教授: | 林浩雄(Hao-Hsiung Lin) |
關鍵字: | 鉍薄膜,物理性質量測系統,霍爾效應,塊材,表面態,反弱局域, Bismuth thin film,PPMS,Hall effect,bulk,surface state,WAL, |
出版年 : | 2020 |
學位: | 碩士 |
摘要: | 本論文以分子束磊晶系統(MBE System)將鉍薄膜成長於輕摻雜矽基板上,透過利用物理性質量測系統(Physics Property Measurement System, PPMS)進行量測,藉由改變溫度以及外加磁場大小,觀察鉍薄膜在不同厚度下磁阻的變化,並嘗試了解塊材(bulk)和表面(surface)的傳輸性質。 我們首先對零磁場下的阻值進行分析,在鉍薄膜較厚的情況下,阻值隨溫度降低所呈現出來的趨勢與大部分的文獻符合,表現出典型的半導體導電機制,而較薄的鉍薄膜在零磁場下隨溫度變化的行為我們猜測有多穩態的結構,會針對高溫和低溫的區域分別進行討論分析。 藉由觀察到低溫高磁場的曲線逐漸飽和的現象,認為趨於飽和的行為是由表面態所貢獻,依此假設,我們將利用three-band transport model對3種不同厚度樣品的變溫霍爾量測結果進行擬合分析,除此之外,我們也假設塊材內部為本質半導體特性,n = p = ni。 結果顯示較厚鉍薄膜的載子遷移率其值約為2000至10000 cm2/Vs,在高溫的區域(100K - 300K)有明顯的T-1.5特性,推測是受到acoustic phonon scattering,低溫的載子遷移率則明顯不隨溫度變化而有所變動,至於載子濃度則是隨溫度降低而下降,其範圍在1x1017 - 3x1018 cm-3,認為費米能階在導電帶,尚未看到能帶打開的現象;較薄的樣品載子遷移率其值可達到80000 cm2/Vs,表面態的載子濃度在低溫大約接近1013 cm-2數量級。 在最薄的10 nm樣品上我們觀測到反弱局域(weak antilocalization, WAL)的現象,藉由引入電子相位相干時間(electron dephasing time, τφ)來探討極低溫環境下的量子傳輸行為。 In this thesis, the Bismuth thin film is grown on lightly doped silicon substrates by molecular beam epitaxy (MBE). The variable temperature and magnetic field is used by Physics Property Measurement System (PPMS). Observe the change of magneto-resistance of the Bismuth thin film under different thickness, and try to understand the transport properties of bulk and surface. We first analyze the resistance value under zero magnetic field. When the Bismuth film is thicker, the trend that the resistance value decreases with the temperature is consistent with most of the literature, showing a typical semiconductor mechanism. As the behavior of the thinner Bismuth film with temperature under zero magnetic field, we guess the Bismuth structure is multi-stable. We will discuss and analyze the high temperature and low temperature regions, respectively. By observing the phenomenon that the curve of low temperature and high magnetic field is gradually saturated, it is believed that the behavior that tends to be saturated is contributed by the surface state. Based on this assumption, we will use the three-band transport model for the variable temperature Hall effect of three samples with different thickness. The measurement results are fitted and analyzed. In addition, we also assume that the interior of the bulk has intrinsic semiconductor characteristics, n = p = ni. The results show that the carrier mobility of the thicker Bismuth film is about 2000 to 10000 cm2/Vs, and it has obvious T-1.5 characteristics in the high temperature region (100K - 300K). Presumably, it is caused by acoustic phonon scattering, and the low-temperature carrier mobility obviously does not change with temperature. As for the carrier concentration, it decreases with the temperature, and its range is 1x1017 - 3x1018 cm-3. It is believed that the Fermi level is in the conductive band, and the phenomenon of band opening has not yet been seen; the carrier mobility of the thinner samples can reach 80000 cm2/Vs, and the carrier concentration in the surface state is approximately the order of 1013 cm-2 at low temperature. We observed weak antilocalization (WAL) phenomenon in the thinnest 10 nm sample. The electron dephasing time (τφ) was introduced to investigate the quantum transport behavior in extremely low temperature environments. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/18099 |
DOI: | 10.6342/NTU202003261 |
全文授權: | 未授權 |
顯示於系所單位: | 光電工程學研究所 |
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