Same Precursor, Two Different Products: Comparing the Structural Evolution of In-Ga-O “Gel-Derived” Powders and Solution-Cast Films Using Pair Distribution Function Analysis

TY - JOUR

T1 - Same Precursor, Two Different Products

T2 - Comparing the Structural Evolution of In-Ga-O “Gel-Derived” Powders and Solution-Cast Films Using Pair Distribution Function Analysis

AU - Wood, Suzannah R.

AU - Woods, Keenan N.

AU - Plassmeyer, Paul N.

AU - Marsh, David A.

AU - Johnson, Darren W.

AU - Page, Catherine J.

AU - Jensen, Kirsten Marie Ørnsbjerg

AU - Johnson, David C

PY - 2017

Y1 - 2017

N2 - Amorphous metal oxides are central to a variety of technological applications. In particular, indium gallium oxide has garnered attention as a thin-film transistor channel layer material. In this work we examine the structural evolution of indium gallium oxide gel-derived powders and thin films using infrared vibrational spectroscopy, X-ray diffraction, and pair distribution function (PDF) analysis of X-ray total scattering from standard and normal incidence thin-film geometries (tfPDF). We find that the gel-derived powders and films from the same aqueous precursor evolve differently with temperature, forming mixtures of Ga-substituted In2O3 and In-substituted β-Ga2O3 with different degrees of substitution. X-ray total scattering and PDF analysis indicate that the majority phase for both the powders and films is an amorphous/nanocrystalline β-Ga2O3 phase, with a minor constituent of In2O3 with significantly larger coherence lengths. This amorphous β-Ga2O3 phase could not be identified using the conventional Bragg diffraction techniques traditionally used to study crystalline metal oxide thin films. The combination of Bragg diffraction and tfPDF provides a much more complete description of film composition and structure, which can be used to detail the effect of processing conditions and structure-property relationships. This study also demonstrates how structural features of amorphous materials, traditionally difficult to characterize by standard diffraction, can be elucidated using tfPDF.

AB - Amorphous metal oxides are central to a variety of technological applications. In particular, indium gallium oxide has garnered attention as a thin-film transistor channel layer material. In this work we examine the structural evolution of indium gallium oxide gel-derived powders and thin films using infrared vibrational spectroscopy, X-ray diffraction, and pair distribution function (PDF) analysis of X-ray total scattering from standard and normal incidence thin-film geometries (tfPDF). We find that the gel-derived powders and films from the same aqueous precursor evolve differently with temperature, forming mixtures of Ga-substituted In2O3 and In-substituted β-Ga2O3 with different degrees of substitution. X-ray total scattering and PDF analysis indicate that the majority phase for both the powders and films is an amorphous/nanocrystalline β-Ga2O3 phase, with a minor constituent of In2O3 with significantly larger coherence lengths. This amorphous β-Ga2O3 phase could not be identified using the conventional Bragg diffraction techniques traditionally used to study crystalline metal oxide thin films. The combination of Bragg diffraction and tfPDF provides a much more complete description of film composition and structure, which can be used to detail the effect of processing conditions and structure-property relationships. This study also demonstrates how structural features of amorphous materials, traditionally difficult to characterize by standard diffraction, can be elucidated using tfPDF.

U2 - 10.1021/jacs.7b02097

DO - 10.1021/jacs.7b02097

M3 - Journal article

C2 - 28328207

AN - SCOPUS:85018473029

SN - 0002-7863

VL - 139

SP - 5607

EP - 5613

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

IS - 15

ER -