(Sn,Al)O_x Films Grown by Atomic Layer Deposition

Abstract

Abstract(Sn,Al)O x composite films with various aluminum (Al) to tin (Sn) ratios were deposited using an atomic layer deposition technique. The chemisorption behavior of cyclic amide of tin(II) and trimethylaluminum were analyzed by Rutherford backscattering spectroscopy. Both precursors showed retarded and enhanced chemisorption on Al 2 O 3 and SnO 2 surfaces, respectively. The films show highly anisotropic electrical conductivity, i.e. much higher resistivity in the direction through the film than parallel to the surface of the film. The cause of the anisotropy was investigated by cross-sectional transmission electron microscopy, which showed a nanolaminate structure of crystalline SnO 2 grains separated by thin, amorphous Al 2 O 3 monolayers. When the Al concentration was higher than ~35 at.%, the composite films became amorphous, and the vertical and lateral direction resistivity values converged toward one value. By properly choosing the ratio of SnO 2 and Al 2 O 3 subcycles, controlled adjustment of film electrical resistivity over more than 15 orders of magnitude was successfully demonstrated.

Band gap engineering of atomic layer deposited ZnxSn1‐xO buffer for efficient Cu(In,Ga)Se2 solar cell

“…Furthermore, the growth rate of the ZTO films at all subcycle ratios was lower than expected considering the rule of mixtures presented by the dashed line. This discrepancy in the growth rate of ternary oxides in ALD was previously reported by Heo et al The significant decrease in the growth rate of ternary oxides relative to their binary oxide constituents has been attributed to a number of reasons including reduced initial reactivity of one precursor on the terminated surface of another precursor and/or reduction in surface reactive species such as hydroxyl groups, and etching of one metal oxide by reactions that occur with the introduction of a second precursor . Figure B showed the variations in the Zn and Sn precursor chemisorption rates as a function of Sn/(Sn + Zn) subcycle ratio.…”

“…Herein, the growth characteristics of ZTO thin films were investigated by using atomic layer deposition (ALD Figure S1. 20 The significant decrease in the growth rate of ternary oxides relative to their binary oxide constituents has been attributed to a number of reasons including reduced initial reactivity of one precursor on the terminated surface of another precursor and/or reduction in surface reactive species such as hydroxyl groups, 21 and etching of one metal oxide by reactions that occur with the introduction of a second precursor. 22 Figure 1B showed the variations in the increased with growth temperature up to 200°C because of the enhanced reactivity at higher temperatures as shown in Figure S2.…”

Organic and inorganic–organic thin film structures by molecular layer deposition: A review

“…Further tuning of material properties may be achieved by combining different inorganic, organic and hybrid layers into various thin-film mixtures, superstructures and nanolaminates. For example, precise control of the refractive index is extremely important in optical applications [ 17 ], while control of the electrical properties is required for storage capacitors, non-volatile memories as well as for transparent thin-film transistors [ 18 – 19 ]. Moreover, the tunability of the surface roughness is advantageous when fabricating gas sensors [ 20 ].…”

Incomplete elimination of precursor ligands during atomic layer deposition of zinc-oxide, tin-oxide, and zinc-tin-oxide

“…However, the composition and combined growth rate during multi-element ALD typically deviate from what is expected from the growth rates of the binary processes, an observation that has been explained in many cases by nucleation effects when switching from one binary process to the other. [6][7][8][9][10][11] Various theories for these deviating trends have been proposed, such as the a) E-mail: sbent@stanford.edu contribution of etching reactions, 9 differences in reactive site densities between the two binary metal-oxide surfaces, 12 or the occurrence of ligand exchange from an adsorbed precursor molecule to a metal surface atom. 13 The deposition of zinc-tin-oxide (ZTO) by ALD has been investigated more extensively than most ternary ALD processes because of its potential applications.…”