1. Sn-Zr-Ch (Ch = S, Se) films by in-situ PLD Andriy Zakutayev 2009 results

2. Experiment Details Thermionics chamber, 10-9 Torr base pressure, 10-7 Torr during ablation a-SiO2 and Si (001) substrates cleaned with methanol and water Target polished after each run and pre-ablated for 1000 pulses Most of the films quenched (~100C/min) PLD parameters varied Studied PLD parameters Temperature Pressure (+ gas type) Target-substrate distance Laser beam intensity Laser repetition rate Type of the substrate Seed layer Target (single phase, SnCh-rich, mixed binary phase) Other investigated processes Chalcogen vapor anneal (CVA) H2Ch flowing gas anneal Rapid thermal anneal

3. Main parameters: Sn-Zr-S Start loosing Sn and S at high T For MFR-500 o C; for VFR-600 o C The loss of Sn is slower than S In MFR (UHV – 1mTorr) P does not matter In VFR (10-100 mTorr) more Sn and S Small distance – re- sputtering and re- evaporation More important for VFR: better-defined plume

4. Main parameters: Sn-Zr-Se Sn- and Se-poor, but stable below 200 o C Fluctuates up to 600 o C Evaporates above 600 o C Oxygen stays constant Mixed phase target – similar trend; need better mixing ratio All ratios increase in VFR (>10 mTorr) Oxygen also increases For Ar/H 2 decreases to 50 mTorr and then increases For reactive Ar/H 2 gas in Sn- Zr-Se the trend is opposite to that for Ar or UHV in Sn-Zr-S Is it Ar – Ar/H2 or S/Se difference or both? Large concentration of oxygen

5. Other parameters Concentration of Sn and S increase with increasing laser beam intensity Upper limit is posed by creation of holes in the target Rather weak dependence on the repetition rate. Sn/Zr changes likely due to temperature variations of the substrate Concentration of Sn and Se do not depend on seed layer and type of the substrate ( or seed layer evaporated..?) Variation in Se/Zr is likely due to different temperature callibrations for a-SiO 2 and c-Si

6. Spatial variation Front/Back variation is abscent No oxygen variation Side (left/right) variation: S/Zr varies by 0.4 Sn/Zr varier by 0.15

7. in-situ: example XRD Sn and (Zr-Se) phases are present Sn/(Zr-Se) decreases with increasing temperature No evidence of SnZrSe3 at any temperature at, 1mTorr of Ar Amorphous at 200C and lower Sn and (Zr-S) phases are present Sn/(Zr-S) increases with increasing pressure Tiny SnZrS3 are present at 100 mTorr, 400C

8. ex-situ: example XRD ZrS peak disappears, but some SnS peaks appear For 100 mTorr film some SnZrS3 present – Sn peak ratio is not correct Sn-Zr-S deposited at 30 o C Anneled with SnZrS3 powder at 400-800 o C Optimum annealing T=700 o C Below and above – ZrS and ZrS 2

9. ex-situ: EPMA results H 2 S anneal replaces S with O in the film Sn content does not change Sealed tube anneal increases S content Sn content stays the same

10. Discussion Possible reasons of non-stoichiometry: (assuming stoichiometric target) Modification of the target during PLD Scattering on the way from to the subsrtate (mass transfer coefficient of Ar/S) Sticking coefficients Re-evaporation Re-sputtering Summary of the main findings: Always Sn- and S-poor: need SnChx- rich or mixed binary phase targets XRD: mainly ZrChx+Sn, rarely and weak SnZrCh3 peaks Transition at 500-600C – lower than synthesis temperature (600 C for SnZrSe3 and 800C for SnZrS3) High pressure: better transfer but hard to control and poor morphology Effect of the target-substrate depends on the gas (inert/reactive) Need denser targets to use larger laser beam intensity No effect of repetition rate, substrate type Quite uniform