Deposition Mechanism and Characterization of Plasma-Enhanced Atomic Layer-Deposited SnO x Films at Different Substrate Temperatures.

The promising functional tin oxide (SnO x ) has attracted tremendous attention due to its transparent and conductive properties. The stoichiometric composition of SnO x can be described as common n-type SnO 2 and p-type Sn 3 O 4 . In this study, the functional SnO x films were prepared successfully by plasma-enhanced atomic layer deposition (PEALD) at different substrate temperatures from 100 to 400 °C. The experimental results involving optical, structural, chemical, and electrical properties and morphologies are discussed. The SnO 2 and oxygen-deficient Sn 3 O 4 phases coexisting in PEALD SnO x films were found. The PEALD SnO x films are composed of intrinsic oxygen vacancies with O-Sn 4+ bonds and then transformed into a crystalline SnO 2 phase with increased substrate temperature, revealing a direct 3.5-4.0 eV band gap and 1.9-2.1 refractive index. Lower (<150 °C) and higher (>300 °C) substrate temperatures can cause precursor condensation and desorption, respectively, resulting in reduced film qualities. The proper composition ratio of O to Sn in PEALD SnO x films near an estimated 1.74 suggests the highest mobility of 12.89 cm 2 V -1 s -1 at 300 °C.