Disorder and instability processes in amorphous conducting oxides

Abstract

The behaviour of ionic amorphous oxide semiconductors (transparent conducting oxides) such as In2O3, SnO2, and ZnO is contrasted with that of covalent amorphous semiconductors such as amorphous Si. These oxides have an s‐like conduction band minima, which leads to high electron mobilities, smaller effects of disorder, and the ability to move the Fermi level well into the conduction band. This results in an absence of the bias stress instability due to the bond breaking mechanism in oxide thin film transistors, which limited the stability of a‐Si:H transistors. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Limits to doping in oxides

“…[9][10][11] The latter applications require an ability to dope the oxide in a unipolar fashion and preferably in a bipolar fashion. The standard transparent conducting oxides can be heavily doped n-type, even in their amorphous phases, because of their ionic bonding, 8,12 in contrast to covalently bonded a-Si, whose doping efficiency is severely impaired in the amorphous phase. 13 Amorphous phases are particularly useful for largearea, low-cost electronics.…”

Optical properties of sputter deposited transparent and conducting TiO2:Nb films

“…All of them have limitations such as uncomfortably narrow ranges of deposition parameters, requirements of high substrate temperatures, cost (for In), etc., and viable alternatives have been sought for many years. A recently discovered alternative is doped TiO 2 [3,4], which is different from the other TCOs in that conduction takes place in the d-band rather than in the s-band [5,6]. Earlier work on TCO-type TiO 2 :Nb has employed pulsed laser deposition [3,[7][8][9][10][11][12][13][14], rf magnetron sputtering [15], and dc magnetron sputtering [11,[16][17][18].…”

X-ray absorption spectroscopy elucidates the impact of structural disorder on electron mobility in amorphous zinc-tin-oxide thin films

“…5) orbitals of metal atoms such as In-5s in a-IGZO. [4][5][6] The spherical symmetry of the s orbitals makes them less prone to form traps and scattering centers when the metal-oxygen-metal bonds are distorted by rotation of metal-oxygen polyhedrons.Amorphous zinc-tin-oxide (a-ZTO) is recently highlighted as a promising candidate material for cost-effective applications, as it is free from toxic and expensive elements (e.g., indium and gallium). Sn] ratio in a-ZTO thin films on device performance suggests a strong correlation between the atomic structure and electronic transport properties of the films.…”

“…5) orbitals of metal atoms such as In-5s in a-IGZO. [4][5][6] The spherical symmetry of the s orbitals makes them less prone to form traps and scattering centers when the metal-oxygen-metal bonds are distorted by rotation of metal-oxygen polyhedrons.…”