Synthesis of titanium phosphide by thermal ALD based on a novel phosphorus precursor

Herein, we present for the first time the synthesis of titanium phosphide (Ti_xP_y) by thermal ALD based on the use of in-house synthesized Tris(trimethyltin)phosphide (TMT₃P) combined with titanium tetrachloride (TiCl₄) as the P- and Ti-precursor, respectively. The deposition process demonstrated followed ALD principles and revealed an ALD window between 175 °C and 225 °C. The Ti_xP_y thin films grown on substrates of different nature were characterized by several techniques, showing granular surfaces and electrical resistivities of the order of hundreds of Ohms. The effects of different ALD parameters such as deposition temperature, dosing time of both precursors, and the type of substrate on the chemical composition were extensively assessed by X-ray photoelectron spectroscopy (XPS). Interestingly, the results yielded the deposition of P-rich titanium phosphide and showed that its chemical composition depends on the deposition temperature and the type of substrate. Based on XPS results, a tentative description of the Ti_xP_y growth as a function of the number of ALD cycles was provided.