Atomic Layer Epitaxy Growth of BaS and BaS:Ce Thin Films from In Situ Synthesized Ba(thd)2

BaS and BaS:Ce thin films were grown by Atomic Layer Epitaxy (ALE) from Ba(thd)2 synthesized in situ during the film growth process by a gas-solid reaction between Hthd and Ba(OH)2. The in situ synthesis avoids problems related to aging of Ba(thd)2 solid source when heated for prolonged times in normal ALE or CVD processes. H2S was used as a sulfur source. Self-limiting film growth with a rate of about 0.8Å/cycle was obtained between 300 and 350°C. The films were polycrystalline and strongly oriented in the (100) direction. BaS:Ce films were deposited using Ce(thd)4 as a dopant source. In photoluminescence these films gave a broad emission spectrum centered around 525 nm. Electroluminescence measurements gave C.I.E. color coordinates x = 0.46 and y = 0.50.