n – p transition sensing behavior of Si-WO 3 film at room temperature

1. n – p transition sensing behavior of Si-WO3film at room temperature

2. WCl6, ethanol • Spin- coat • P-Si, Al2O3 • Anneal at 300℃, 400℃, 500℃ for 2h at ambient atmosphere

3. Fig.1 S2: Si-WO3 400℃ S1: Si-WO3 300℃ S4: Al2O3-WO3 400℃ S3: Si-WO3 500℃

4. Fig.2 Relationship between operating temperature and sensitivity for S1, S2,S3 and S4 to 2ppm NO2 S1 S2 S3 S4

5. Fig.3 Dynamic response (a, c) S2 at RT, (b, d) S4 at 200℃ (a) (b) NO2 NO2 (c) (d) NH3 NH3

6. Fig.4 Response/Recovery time of S2to 2ppm NO2 at RT 9s

7. Table 1 Response/Recovery time of S2to 2ppm NO2 at RT

8. Fig.5 Selectivity. S2to 100ppm acetone, alcohol, ammonia and 2ppm NO2 at RT

9. Fig.6 p – Si n- WO3 p – Si n- WO3 ,oxygen vacancies; O0, the oxygen atom in an oxygen site