Postdeposition annealing on RF-sputtered SrTiO3 thin films

Understanding of structural, optical, and electrical properties of thin films are very important for a reliable device performance. In the present work, the effect of postdeposition annealing on stoichiometric SrTiO3 (STO) thin films grown by radio frequency magnetron sputtering at room temperature on p-type Si (100) and quartz substrates were studied. Highly transparent and well adhered thin films were obtained in visible and near infrared regions. As-deposited films were amorphous, while nanocrystalline and polycrystalline phases of the STO thin films formed as a function of annealing temperature. Films annealed at 300 �C showed nanocrystallinity with some amorphous phase. Crystallization started after 15 min annealing at 700 �C, and further improved for films annealed at 800 �C. However, crystallinity reduced for films which were annealed at 900 �C. The optical and electrical properties of STO thin films affected by postdeposition annealing at 800 �C: Eg values decreased from 4.50 to 4.18 eV, n(λ) values (at 550 nm) increased from 1.81 to 2.16. The surface roughness increased with the annealing temperature due to the increased crystallite size, densification and following void formation which can be seen from the scanning electron microscopy images. The highest dielectric constants (46 at 100 kHz) observed for films annealed at 800 �C; however, it was lower for 300 �C annealed (25 at 100 kHz) and as-deposited (7 at 100 kHz) STO films having ∼80 nm thickness. � 2017 American Vacuum Society

All-Silicon Ultra-Broadband Infrared Light Absorbers

Absorbing infrared radiation efficiently is important for critical applications such as thermal imaging and infrared spectroscopy. Common infrared absorbing materials are not standard in Si VLSI technology. We demonstrate ultra-broadband mid-infrared absorbers based purely on silicon. Broadband absorption is achieved by the combined effects of free carrier absorption, and vibrational and plasmonic absorption resonances. The absorbers, consisting of periodically arranged silicon gratings, can be fabricated using standard optical lithography and deep reactive ion etching techniques, allowing for cost-effective and wafer-scale fabrication of micro-structures. Absorption wavebands in excess of 15 micrometers (5-20 μm) are demonstrated with more than 90% average absorptivity. The structures also exhibit broadband absorption performance even at large angles of incidence (θ = 50°), and independent of polarization. © 2016 The Author(s)