Carrier transport by field enhanced thermal detrapping in Si nanocrystals thin films

Abstract

Postdeposition thermal annealing and material stability of 75 °C hydrogenated nanocrystalline silicon plasmaenhanced chemical vapor deposition films J. Appl. Phys. 98, 034305 (2005); 10.1063/1.1993777 Schottky junction properties on high quality boron-doped homoepitaxial diamond thin filmsThe carrier transport at high voltage region in Si nanocrystal ͑SiNC͒ thin films has been investigated. The current-voltage measurements demonstrate that at high voltage region, conductance exponentially depends on V 1/2 . The activation energy, measured from the temperature dependence of the current-voltage ͑I-V͒ characteristics, decreases with an increase in the applied voltage. These results indicate that field enhanced detrapping dominates transport mechanism in the SiNC films at high voltage region. The possible influence of metal/semiconductor contacts on V 1/2 dependence has been excluded through the activation energy measurement on different work-function metals as electrodes. The position of the traps contributing to the detrapping processes is concluded to be at interfaces of SiNC/ SiO 2 since H 2 annealing drastically decreases the activation energy. The reasons why experimental results demonstrate no accordance with the material parameter V ‫ء‬ of Poole-Frenkel expression have been discussed based on nanostructure characteristics of SiNC film.

Nonthermal Plasma Synthesis of Nanocrystals: Fundamental Principles, Materials, and Applications

“…Once particles reached the desired size, they were extracted from the plasma cell by a pulse of hydrogen gas . As shown in Figure , the nanocrystals left the plasma cell through an orifice and enter an ultrahigh vacuum chamber where they were deposited on a substrate to fabricate thin films. − In a recent study, the authors used emission spectroscopy to characterize this plasma . They noticed that there was a clear correlation between the increase in argon line intensity and the generation of silicon nanocrystals.…”

Fabrication of Flexible and Vertical Silicon Nanowire Electronics

“…Porous Si has been shown to have nonlinear I – V characteristics − and resistivity values 5 orders of magnitude larger than crystalline silicon due to the depletion of free charge carriers. , Upon closer investigation of the porous SiNW device I – V curves, it was found that at higher voltages the conductance ( I / V ) shows an exponential dependence on the square root of applied voltage, as shown in Figure c, and such dependence is best described by the Poole–Frenkel relationship shown in eqs and : G ( V , T ) = G o exp [ − E A k B T ] exp true[ V V * true] 1 / 2 V * = k normalB T e / true[ e π ε d true] 1 / 2 Here, G is the conductance of porous Si, G o is the conductance prefactor, E A is the activation energy to release a trapped charge carrier from Coulombic traps, k B is the Boltzmann’s constant, T is the device temperature, V is the applied voltage, V * is a parameter reflecting the material characteristic, e is the elementary electron charge, ε is the dielectric constant, and d is the length of the porous channel. The Poole–Frenkel relationship attributes the nonlinear I – V characteristics to an electric-field-enhanced thermal excitation of charge carriers from Coulombic traps, for which the activation energy to release a trapped carrier is reduced with increasing electric fields, leading to the nonlinear voltage dependence. ,,− At low voltages, the metal–porous Si contacts will exhibit a quasi-ohmic contact, corresponding to the low-voltage ...…”

“…25 Nevertheless, as the voltage is increased in the porous SiNWs, the electric field enhances the thermal excitation of charge carriers from Coulombic traps, causing the conductance (G) to increase with V in the form of exp(V 1/2 ). 32,40 To confirm this behavior associated with porous SiNWs, we calculated the activation energy associated with releasing trapped carriers by the slope of the zero-field conductance values vs 1/T curve (Figure 4d) using the Arrhenius relation according to eq 1, where the zerofield conductances at any specified temperature were obtained by extrapolating the conductances measured under different bias to zero bias (Figure 4c, marked by the open red circles) at that temperature. As a result, the obtained activation energy is about 0.25 eV from Figure 4d and generally in the range of 0.23 − 0.32 eV, which is comparable to the 0.14−0.5 eV activation energies for bulk porous Si films formed by anodization using the same Poole−Frenkel relation.…”

Charge transport in nanoparticular thin films of zinc oxide and aluminum-doped zinc oxide

“…30,31 In those reports, the experimentally and theoretically derived values of 3 r , which directly correlate with b, were completely different. It was argued that the theory behind the PF effect might not be adaptable to nanostructured lms, because these lms would not provide a straight-forward physical meaning of 3 r .…”

“…for nanostructured lms of silicon. Besides hopping, 27,28 SCLC, 29 the Poole-Frenkel effect, 30,31 and tunnelling 32,33 were reported for nano-Si (porous silicon or nanoparticles). These inconsistent results further emphasize the need for a detailed description of charge transport in nanoparticular lms.…”