Photoconductivity: A probe of defect states in carbon aerogels

Autor:	R.W. Pekala, M. S. Dresselhaus, Gillian A. M. Reynolds, A. W. P. Fung, Zhe Wang
Rok vydání:	1994
Předmět:	Colloid Materials science chemistry Screening effect Electrical resistivity and conductivity Photoconductivity Analytical chemistry chemistry.chemical_element Aerogel Dark conductivity Carbon
Zdroj:	Physical Review B. 49:15027-15034
ISSN:	1095-3795 0163-1829
DOI:	10.1103/physrevb.49.15027
Popis:	The photoconductivity and dark conductivity of carbon aerogels with various heat-treatment temperatures, [ital T][sub HT], and densities are studied. Unlike the trend for as-prepared samples, the magnitude of the photoconductivity for heat-treated ([ital T][sub HT][gt]1050 [degree]C) carbon aerogel samples decreaes as the sample density and heat-treatment temperature increase. We propose a model which quantitatively explains the observed temperature dependence of the photoconductivity data. Based on this model, we attribute the observed photoconductivity to photoholes present in the system. The number of defect states and their corresponding energy decrease with increasing [ital T][sub HT] and increasing density. The decrease in the energy is attributed to a decrease in the screening effect of the defects on trapped charges. The effect of increasing the heat-treatment temperature causes the structure of the carbon aerogel to become more graphitic, especially for aerogel samples with higher mass density.
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_dedup___::70e5f9be8e769c780ef3c072943e0037 https://doi.org/10.1103/physrevb.49.15027 Zobrazit plný text záznamu