本研究利用分子束磊晶（Molecular Beam Epitaxy, MBE）技術，於藍寶石（Al₂O₃）基板上成長厚度為 4 nm 與 8 nm 的硒化鉍（Bi₂Se₃）拓樸絕緣體薄膜，並進行 10–300 K 變溫磁傳輸量測，以分析其縱向電阻、霍爾效應、載子濃度、霍爾遷移率及弱反局域化特性。

量測結果顯示，兩種厚度樣品皆呈現 n 型傳輸，片載子濃度皆位於 10¹³ cm⁻² 數量級，未隨厚度呈現明顯變化。8 nm 樣品於各溫度下的霍爾遷移率皆高於 4 nm 樣品，約為其 1.8 至 2.1 倍，顯示較薄薄膜可能受到較強的表面、界面及缺陷散射影響。此外，兩種樣品的縱向電阻皆隨溫度升高而增加，呈現金屬型傳輸行為。

4 nm 樣品於低磁場下呈現明顯的弱反局域化特徵。經 Hikami–Larkin–Nagaoka（HLN）模型擬合，10 K 時 α 約為 −0.481，相位相干長度約為 145.3 nm，且隨溫度升高，相位相干長度逐漸縮短，弱反局域化效應亦隨之減弱。8 nm 樣品因縱向電阻訊號具有較明顯的不規則起伏，因此未進行 HLN 擬合。

綜合而言，Bi₂Se₃ 的薄膜厚度可能對載子遷移率具有明顯影響，研究結果可作為後續探討其厚度效應與表面態傳輸特性的參考

This study investigates the temperature-dependent magnetotransport properties of 4 nm and 8 nm Bi₂Se₃ topological insulator thin films. The films were grown on sapphire substrates by molecular beam epitaxy and fabricated into Hall-bar devices. Magnetotransport measurements were performed from 10 to 300 K with the magnetic field perpendicular to the film surface.
Both samples exhibited n-type transport, with sheet carrier concentrations on the order of 10¹³ cm⁻² and no clear thickness dependence. The Hall mobility of the 8 nm sample was approximately 1.8–2.1 times higher than that of the 4 nm sample, suggesting stronger surface, interface, and defect scattering in the thinner film. Both samples showed metallic transport behavior, as the longitudinal resistance increased with temperature.
The 4 nm sample exhibited a clear weak antilocalization feature at low magnetic fields. Hikami–Larkin–Nagaoka fitting yielded an α value of approximately −0.481 and a phase coherence length of 145.3 nm at 10 K. The phase coherence length and weak antilocalization effect decreased with increasing temperature. The 8 nm sample was not fitted because of irregular fluctuations in the longitudinal resistance signal.
These results suggest that film thickness may influence carrier mobility and low-temperature quantum transport in Bi₂Se₃ thin films.

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