From Molecular Gallium and Indium Siloxide Precursors to Amorphous Semiconducting Transparent Oxide Layers for Applications in Thin‐Film Field‐Effect Transistors

Abstract

Abstract The syntheses, structural characterization, and thermal degradation of a series of the new indium and gallium siloxide dimers [{Me 2 In(OSiEt 3 )} 2 ] ( 1 ), [{Me 2 Ga(OSiEt 3 )} 2 ] ( 2 ), [{Me 2 In(OSi(O t Bu) 3 )} 2 ] ( 3 ), [{Me 2 Ga(OSi(O t Bu) 3 )} 2 ] ( 4 ), and In[OSi(O t Bu) 3 )] ( 5 ) is reported. Compounds 1 – 4 are readily accessible by facile Brönsted reaction of InMe 3 or GaMe 3 with the corresponding silanols Et 3 SiOH and ( t BuO) 3 SiOH, respectively. Compound 5 could be obtained by analogous protolysis of [In{N(SiMe 3 ) 2 } 3 ] with an excess amount of ( t BuO) 3 SiOH. The suitability of 1 – 5 to serve as molecular precursors for low‐temperature synthesis of amorphous indium and gallium oxide for electronic applications was probed. Thus their thermal degradation was studied by Thermogravimetric/differential thermogravimetry analysis (TGA/DTG). Compounds 1 – 4 were decomposed under dry synthetic air (20 % O 2 , 80 % N 2 ) at low temperature to yield amorphous indium oxide and gallium oxide particles, respectively. In contrast, thermal degradation of 5 affords amorphous indium silicate. All of these products were analyzed by multiple techniques including powder X‐ray diffraction analysis (PXRD) , transmission electron microscopy (TEM), and energy dispersive X‐ray spectroscopy (EDX). Thin‐film field‐effect transistors (FETs) could be fabricated through spin‐coating of silicon‐wafers with solutions of 1 in toluene and subsequent calcination under dry synthetic air at 350 °C. These films exhibit very good FET performance with a field‐effect mobility of 3.0×10 −1 cm 2 V −1 s and an on/off current ratio of 10 8 .