Abstract
Selective UV sensitivity was observed in Metal-Oxide-Semiconductor structures with Si nanoclusters. Si nanocrystals and amorphous Si nanoparticles (a-Si NPs) were obtained by furnace annealing of SiOx films with x = 1.15 for 60 min in N2 at 1000 and 700 °C, respectively. XPS and TEM analysis prove phase separation and formation of Si nanocrystals in SiO2, while the a-Si NPs are formed in SiO1.7 matrix. Both types of structures show selective sensitivity to UV light; the effect is more pronounced in the structure with nanocrystals. The responsivity of the nanocrystal structure to 365 nm UV light is ~ 4 times higher than that to green light at 4 V applied to the top contact. The observed effect is explained by assuming that only short wavelength radiation generates photocarriers in the amorphous and crystalline nanoclusters.
Highlights
Metal-Oxide-Semiconductor (MOS) structures with silicon nanocrystals have been actively studied for electronic and optoelectronic applications in the past decades [1,2,3,4]
Selective UV sensitivity has been found in MOS structures with silicon nanocrystals in a SiO2 matrix and amorphous Si nanoparticles in a SiO1.7 matrix
It was estimated that the material with a-Si nanoparticles responds to wavelengths close to or smaller than 480 nm, while the material with nanocrystals responds to wavelengths ≤ 690 nm
Summary
Metal-Oxide-Semiconductor (MOS) structures with silicon nanocrystals have been actively studied for electronic and optoelectronic applications in the past decades [1,2,3,4]. The processes of formation of silicon nanoclusters (Si NCs) in MOS structures are compatible with today’s microelectronic technology, which make them applicable in floating gate non-volatile memory devices [1,4], Si based light emitters [5,6] and “third generation” solar cells [7]. UV enhanced silicon photodiodes are well-established devices for UV detection [8], they have the drawback to respond to low energy radiation. Since the Si bandgap is ~1.1 eV these photodiodes require filters to block out the visible and infrared photons. Sheng et al have published results for a visible blind Si based UV detector that uses down-shifting luminophore, which absorbs in the 250–360 nm range and Sensors 2019, 19, 2277; doi:10.3390/s19102277 www.mdpi.com/journal/sensors
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