Contents lists available at ScienceDirect Progress in Solid State Chemistry journal homepage: www.elsevier.com/locate/pssc Mass spectrometry drives stoichiometric GaAs formation from single-source precursors Anatoliy Sokolov a,* , Bruce Gerhart b , Robert J. Wright c , Anna M. Zink a , George L. Athens a , Steve Rozeveld b , Arkady L. Krasovskiy c , Liam P. Spencer c , Robert Froese a , Peter Nickias a , James C. Stevens c a The Dow Chemical Company, 1776 Building, Midland, MI 48674, United States b The Dow Chemical Company, 1897 Building, Midland, MI 48674, United States c The Dow Chemical Company, 230 Abner Jackson Parkway, Lake Jackson, TX 77566, United States ABSTRACT Evolved gas analysis (EGA) mass-spectrometry (MS) is used to characterize the solid state pyrolysis decom- position pathways of air- and moisture-sensitive organometallic compounds. In this study, the single-source GaAs compounds (Et 2 AsGaEt 2 ) 3 (1),(t-Bu 2 AsGaEt 2 ) 2 (2), and [t-Bu(H)AsGaEt 2 ] 2 (3) were heated in capillary tubes under inert condition and the volatile products were analyzed by MS. In addition, the relative ratios of evolved gases were characterized using gas chromatography (GC), while the solid state pyrolysis products were analyzed by EDS, 1 H NMR and XRD. Pyrolysis of GaAs single-source materials in the solid state reveals chemical information on the stability of the GaeAs bond, an observation masked in gas-phase analysis of single-source materials during chemical vapor deposition. Information on GaeAs bond stability may be elucidated due to the volatility of the by-products formed during Ga-As precursor pyrolysis. Loss of GaeAs bond integrity in materials with alkyl substitution on Ga and As leads to formation of mobile and volatile alkyl diarsine species, as was observed for the pyrolysis of 1. An in-situ method to monitor solid-state pyrolysis by mass spectrometry identified the loss of a tetraalkyl-diarsine as the critical factor that drives formation of sub-stoichiometric GaAs products from single-source precursors. Replacing a single alkyl group on the As atom with a H (precursor 3) leads to the loss of an alkane instead of tetraalkyl-diarsine formation. Solid-state pyrolysis precursor 3 results in the for- mation of polycrystalline GaAs in up to 58% yield with a 52:48 Ga:As stoichiometry. Introduction Gallium arsenide (GaAs) is an interesting material with applications in mobile phones, laser diodes, high frequency radar, microwave gen- erators, and solar cells. Single junction photovoltaic devices based on GaAs have recently reached a record 28.8% conversion efficiency, which approaches the Shockley-Queisser limit [1]. A limitation to the use of GaAs is the high cost of single-crystal GaAs wafers. In general, GaAs photovoltaic cells are fabricated using AsH 3 and GaMe 3 via a metal-organic chemical vapor deposition process (MOCVD) which re- sults in epitaxial growth of p- and n-type GaAs [2]. It has been shown that epitaxial GaAs can also be grown using single-source precursors in MOCVD [3–7], CBE [8,9], low pressure chemical vapor deposition [3], spray pyrolysis [10], or supersonic jet techniques [11]. The use of single-source precursors is attractive because, in concept, the GaAs stoichiometry may be controlled by chemically bonding the two elements together. Studies on the decomposition pathway of single- source GaAs precursors have involved either high vacuum experiments (CVD process) [12] or headspace analysis of pyrolysis in closed-vessels [13]. A potential pathway to lower the cost of gas-phase deposition is to pyrolyze single-source GaAs precursors from the solid state. However, while chemical solution deposition methods have been used with single-source precursors to make oxides [14,15] and perovskites [16,17], mechanisms for single-source GaAs pyrolysis are not well un- derstood. In this paper, a novel approach is presented that combines in- situ evolved gas analysis mass spectrometry (EGA/MS), 1 H NMR, X-ray powder diffraction (XRD) and energy dispersive spectroscopy (EDS) to elucidate the solid-state decomposition pathways for Ga-As based ma- terials. The insights and molecular design principles provided by de- composition pathway analysis are applied to form stoichiometric GaAs through solid-state pyrolysis of a novel precursor. http://dx.doi.org/10.1016/j.progsolidstchem.2017.10.002 * Corresponding author. E-mail address: ansokolov@dow.com (A. Sokolov). Progress in Solid State Chemistry xxx (xxxx) xxx–xxx 0079-6786/ © 2017 Elsevier Ltd. All rights reserved. Please cite this article as: Sokolov, A., Progress in Solid State Chemistry (2017), http://dx.doi.org/10.1016/j.progsolidstchem.2017.10.002