Studies on the Influence of Growth Time on the Rutile TiO 2 Nanostructures Prepared on Si Substrates with Fabricated High-Sensitivity and Fast-Response p-n Heterojunction Photodiode

Abstract

In this study, the effect of duration on the growth of rutile TiO2 nanostructures (Ns) deposited onto the p-Si (111) substrate on the structural, morphological, and optical properties of rutile TiO2 Ns has been investigated. All Si substrates were seeded with a TiO2 seed layer synthesized using a radio-frequency (RF) reactive magnetron sputtering system. Chemical bath deposition method (CBD) was employed to grow rutile TiO2 Ns on seeded Si substrates at duration time of growth (1, 2, 3, and 4 h). X-ray diffraction, Raman spectroscopy,and field-emission scanning electron microscopy (FESEM) analyses demonstrated the tetragonal rutile structure of the synthesized TiO2 Ns with the highest (110) peak intensity. Optical properties were investigatedby using photoluminescence (PL) spectroscopy of the grown rutile Ns, with the spectra exhibiting the sharpest (smallest FWHMs) and highest peak revealed the high quality of TiO2 Ns with few defects was found for the sample prepared for 3 h, which reflects the crystalline quality. These results show that the optimized growth conditions yield very high quality TiO2 Ns on p-type (111)-oriented silicon substrates. A fast-response p-n heterojunction photodiode was fabricated by depositing Al contacts on the front of the optimal sample via RF reactive magnetron sputtering. Upon illumination of a pulsed UV light (325 nm, 1.6 mW/cm2) at 5 V bias voltage, the device showed 3.8 × 102 sensitivity, the photoresponse peak was 460 mA/W, the response and recovery times were 50.8 and 57.8 ms, respectively.