Determination of surface recombination velocities of organic monolayers on silicon through Kelvin probe

Abstract

We report the determination of surface recombination velocity of electron-hole pairs for silicon samples passivated with organic monolayers by using the Kelvin probe. The recombination velocity was determined by monitoring the surface photovoltage as a function of the incident photon flux. By scanning of the Kelvin probe tip over the sample area, the change in surface recombination velocity can be measured allowing mapping of the recombination 2 lifetimes. Organic monolayers with different chain lengths and exhibiting various recombination lifetimes were synthesized through a two-step chlorination-alkylation technique. The estimated recombination lifetimes were compared against those obtained from an industrial standard technique using a Sinton WCT-120 and were found to be in good agreement.INTRODUCTION:

Silicon photosensitisation using molecular layers

“…48,49 Surface photovoltage (SPV) measurements on methyl terminated Si(111) surfaces have revealed unusually large SPV signals that can only be explained by charge accumulation in the Si(111) interface during the alkylation procedure. [47][48][49][50][51][52] Similar surface chemistry treatments have resulted in a p/n junction near the surface of silicon. 53 The passivation properties of the methyl, vinyl and allyl terminated silicon surfaces were investigated by measuring the silicon emission spectra and decay curves (Fig.…”

Functionalization of Oxide‐Free Silicon Surfaces for Biosensing Applications

“…[142] As the native oxide grow on the hydrogen terminated silicon, defects are introduced that dramatically increases the velocity with several orders of magnitude up to 10 6 cm s −1 . [143] Organic monolayer on oxide free silicon surfaces have appeared to generate few defects with low recombination velocities in the order of 10 2 cm s −1 , enough to generate an efficient photocurrent. [143] Alkyl monolayers generally yield a maximum coverage of ≈50% of the reactive SiH sites, bulkier molecules even lower.…”

“…[ 142 ] As the native oxide grow on the hydrogen terminated silicon, defects are introduced that dramatically increases the velocity with several orders of magnitude up to 10 6 cm s −1 . [ 143 ]…”

“…[143] Organic monolayer on oxide free silicon surfaces have appeared to generate few defects with low recombination velocities in the order of 10 2 cm s −1 , enough to generate an efficient photocurrent. [143] Alkyl monolayers generally yield a maximum coverage of ≈50% of the reactive SiH sites, bulkier molecules even lower. [17,69] Thus a dense interlayer that prevents penetration of water molecules that may cause oxidation and introduce surface defects is crucial for the device performance.…”