Electrical and Optical Characteristics of Si-Nanoparticle Films Deposited onto Substrates by High-Voltage Electrospraying from Ethanol Sols

Journal Article · Mon Apr 15 00:00:00 EDT 2019 · Semiconductors (Woodbury, N.Y., Print)

DOI:https://doi.org/10.1134/S1063782619040158· OSTI ID:22945024

Davydova, D. V.; Bubenov, S. S.; Dorofeev, S. G. ^[1]

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1. Moscow State University, Faculty of Chemistry (Russian Federation)

The optical and electrical characteristics of films consisting of nanocrystalline silicon (nc-Si) deposited onto substrates by the high-voltage electrospraying of nc-Si sols in ethanol are investigated. It is found that the interaction of ethanol droplets carrying Si nanoparticles with a corona-discharge electric field leads to the polymerization of ethanol and the formation of a polymer layer on the Si-nanoparticle surface. A high-voltage facility for depositing the films using an additional focusing electrode allows one to change the geometry of the electric field and intensity in the region of the ethanol droplet flow. As a result, nc-Si films with qualitatively different properties of the polymer on the nanoparticle surface are formed, specifically, nc-Si-A and nc-Si-B, obtained without a focusing electrode and with it, respectively. Upon annealing at temperatures of up to 400°С, the optical band gap E{sub g} of the nc-Si-A films increases from ~1.9 to ~2.2 eV, while the E{sub g} value of the nc-Si-B films remains constant and amounts to 1.85 eV. The constant E{sub g} value of the nc-Si-B films is explained by the properties of the polymer on the Si-nanoparticle surface and the more effective blocking of oxygen penetration from the surrounding environment upon annealing at temperatures of up to 400°C than in the case of a polymer in nc-Si-A films. The temperature dependences of the dark and photoinduced conductivity of nc-Si-A films are approximated with good accuracy by two activation-type exponential functions and the dark activation energies are ~0.75 and 0.1 eV, respectively. The conductivity of the nc-Si-A films noticeably decreases under irradiation of the samples at wavelengths of 460–470 nm. The temperature dependences of the conductivity of the nc-Si-B films are approximated with good accuracy by exponential functions with activation energies of 0.73 (in the dark) and 0.59 eV (under photoexcitation). In contrast to the case of nc-Si-A films, the photoconductivity of nc-Si-B films grows more than fourfold relative to the dark conductivity under analogous illumination. The nc-Si-B films are photoactive and sandwich-like Al/nc-Si-B/Al structures can generate a voltage. The dark conductivity and photoconductivity of the nc-Si-A films in the voltage range of V > 2 V are determined by the two-center Poole–Frenkel effect; the concentration of the centers affecting the Poole–Frenkel conductivity is ~3 × 10{sup 17} cm{sup –3}. In nc-Si-B films in the voltage range of 2–5 V, electron transport is determined by space-charge-limited currents and, at high voltages, by the two-center Poole–Frenkel effect. The concentration of traps contributing to the space-charge-limited currents is ~4 × 10{sup 16} cm{sup –3}. The concentration of Poole–Frenkel centers affecting the conductivity decreases according to the activation law with an activation energy of 0.7 eV from 3 × 10{sup 16} to 2 × 10{sup 14} cm{sup –3} with a decrease in temperature from 120°C to 40°C.

• OSTI ID: 22945024
• Journal Information: Semiconductors (Woodbury, N.Y., Print), Vol. 53, Issue 4; Other Information: Copyright (c) 2019 Pleiades Publishing, Ltd.; Country of input: International Atomic Energy Agency (IAEA); ISSN 1063-7826
• Country of Publication: United States
• Language: English

Related Subjects

77 NANOSCIENCE AND NANOTECHNOLOGY
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ACCURACY
ACTIVATION ENERGY
ANNEALING
CONCENTRATION RATIO
CORONA DISCHARGES
DEPOSITION
DROPLETS
ELECTRIC FIELDS
ELECTRIC POTENTIAL
ELECTRODES
ELECTRON TRANSFER
ETHANOL
FOCUSING
FUNCTIONS
GEOMETRY
ILLUMINANCE
NANOCRYSTALS
NANOPARTICLES
OXYGEN
PHOTOCONDUCTIVITY
POLYMERIZATION
POLYMERS
SILICON
SOLS
SPACE CHARGE
TEMPERATURE DEPENDENCE
THIN FILMS
TRAPS
WAVELENGTHS