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2D Electron Gas at the Interface of Atomic‐Layer‐Deposited Al 2 O 3 /TiO 2 on SrTiO 3 Single Crystal Substrate
Author(s) -
Lee Hyun Jae,
Moon Taehwan,
An Cheol Hyun,
Hwang Cheol Seong
Publication year - 2019
Publication title -
advanced electronic materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.25
H-Index - 56
ISSN - 2199-160X
DOI - 10.1002/aelm.201800527
Subject(s) - materials science , amorphous solid , anatase , x ray photoelectron spectroscopy , thin film , substrate (aquarium) , crystallinity , analytical chemistry (journal) , layer (electronics) , atomic layer deposition , crystal (programming language) , conductivity , crystallography , nanotechnology , chemical engineering , chemistry , composite material , photocatalysis , oceanography , programming language , chromatography , geology , catalysis , biochemistry , computer science , engineering
The presence of 2D electron gas (2DEG) at the interface between an amorphous Al 2 O 3 ( a ‐AO) thin film and an anatase TiO 2 (TO) thin film is demonstrated. The a ‐AO and TO thin films are prepared via atomic layer deposition on a SrTiO 3 (STO) single crystal substrate. The reduction of the TO surface during the a ‐AO deposition produces oxygen vacancies, which are effective electron donors. The systematic analysis of the physical properties of the TO layer reveals that the crystallinity of the TO layer affects the conductivity, carrier concentration and the mobility of the 2DEG, and also the critical a ‐AO thickness, which is the minimum thickness for exhibiting the apparent conductivity. The 2DEG between the a ‐AO and the sufficiently thick TO layer exhibits an almost two‐orders‐of‐magnitude‐higher carrier concentration (≈10 14 cm ‐2 ) than the previously reported 2DEG at a ‐AO/STO, while the mobility (≈10° cm 2 V ‐1 s ‐1 ) is relatively low. Also, angle‐resolved X‐ray photoelectron spectroscopy elucidates the spatial distribution and atomic ratio of the reduced Ti ions. Due to the increasing fraction of the anatase phase in the TO layer, the oxygen vacancies are prone to ionize, and the carriers are better confined to the interface, making them more 2DEG‐like.