布里渊区
角分辨光电子能谱
凝聚态物理
铁电性
材料科学
电子
费米能级
范德瓦尔斯力
密度泛函理论
电子能带结构
带隙
电子结构
物理
光电子学
电介质
量子力学
分子
作者
Geoffroy Kremer,Aymen Mahmoudi,Adel M’Foukh,Meryem Bouaziz,Mehrdad Rahimi,Maria Luisa Della Rocca,P. Le Fèvre,Jean‐François Dayen,F. Bertran,Sylvia Matzen,Marco Pala,Julien Chaste,Fabrice Oehler,Abdelkarim Ouerghi
出处
期刊:ACS Nano
[American Chemical Society]
日期:2023-08-16
卷期号:17 (19): 18924-18931
标识
DOI:10.1021/acsnano.3c04186
摘要
Two-dimensional (2D) ferroelectric (FE) materials are promising compounds for next-generation nonvolatile memories due to their low energy consumption and high endurance. Among them, α-In2Se3 has drawn particular attention due to its in- and out-of-plane ferroelectricity, whose robustness has been demonstrated down to the monolayer limit. This is a relatively uncommon behavior since most bulk FE materials lose their ferroelectric character at the 2D limit due to the depolarization field. Using angle resolved photoemission spectroscopy (ARPES), we unveil another unusual 2D phenomenon appearing in 2H α-In2Se3 single crystals, the occurrence of a highly metallic two-dimensional electron gas (2DEG) at the surface of vacuum-cleaved crystals. This 2DEG exhibits two confined states, which correspond to an electron density of approximately 1013 electrons/cm2, also confirmed by thermoelectric measurements. Combination of ARPES and density functional theory (DFT) calculations reveals a direct band gap of energy equal to 1.3 ± 0.1 eV, with the bottom of the conduction band localized at the center of the Brillouin zone, just below the Fermi level. Such strong n-type doping further supports the quantum confinement of electrons and the formation of the 2DEG.
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