Overcharging of porous silicon localized states at gas adsorption

Abstract

The behaviour of localized states in Pd/nano-or mesoporous Si/p-Si heterojunctions is studied by the DLTS technique in a vacuum and different atmospheres: ambient air, Ar, N 2 , CO 2 , O 2 . The complex DLTS spectra of both signs related to electron and hole traps in porous Si are detected. The intensity of DLTS peaks and activation energy is shown to be dependent on the morphology of the porous layers and ambient atmosphere in which DLTS measurements were carried out. The shift of activation energy with increase of the applied reverse voltage is interpreted from the point of view of a spatially inhomogeneous distribution of localized states in a porous layer. The cyclic transformation of DLTS spectra is observed for consecutive measurements in a vacuum and ambient atmosphere. Oxygen adsorption (at partial pressure of a few mbar) results in strong passivation of deep traps in mesoporous Si.

Method for Determination of Characteristics of Sensors Based on Electroconducting Polymers

“…There is the dependence of adsorption effect (I-I o )/I o on applied voltage, when (I-I o )/I o decreases at the increase of forward voltage biases, and linear dependence of (I-I o )/I o on hydrogen concentration (Fig.4). To explain the experimental results we account the surface states insides of pores and/or at PS-Si and PS-SiO 2 interfaces that was done before in [14,15]. …”

Thermally induced acoustic waves in porous silicon

“…Since the surface area inside pores is much more in comparing with one of flat Al contact, the adsorption process occurs mainly inside the pores. This is one of the reasons on high gas sensing of metal/PS/c-Si heterostructures at the electrical measurements [9,10].…”

“…The involved sensor mechanism is explained, commonly, in the terms of charge carriers density change in the porous layer caused to the adsorbed molecules, or dielectric constant increment under gas adsorption in the pores [10][11][12].…”

IMPACT OF GAS ADSORPTION AND pH OF SOLUTIONS ON RADIATIVE LIFETIME OF MODIFIED POROUS SILICON LAYERS

“…The oxidized and covered by PEDOT samples display better sensitivity and stability to pH change. The possible explanation of sensitivity increasing is the swelling of the polymer insides the pores [10], increasing capillary condensation effects or passivation effects [11,12]. …”