Conduction and Excess Charge in Silicate Glass/Air Interfaces

Autor(es)

Paiva, Victor T. C. ^[1] ; Santos, Leandra P. ^[1] ; da Silva, Douglas S. ^[1] ; Burgo, Thiago A. L. ^[2] ; Galembeck, Fernando ^[1]

Afiliação do(s) autor(es)

^[1] Univ Estadual Campinas, Inst Chem, BR-13083970 Campinas, SP - Brazil

^[2] Univ Fed Santa Maria, Dept Phys, BR-97105900 Santa Maria, RS - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Langmuir; v. 35, n. 24, p. 7703-7712, JUN 18 2019.
• Citações Web of Science: 1

Resumo

The glass/air interface shows electrical properties that are unexpected for a widely used electrical insulator. The mobility of interfacial charge carriers under 80% relative humidity (RH) is 4.81 X 10(-5) m(2) s(-1), 3 orders of magnitude higher than the electrophoretic mobility of simple ions in water and less than 2 orders of magnitude lower than the electron mobility in copper metal. This allows the glass/air interface to reach the same potential as a biased contacting metal quickly. The interfacial surface resistance R increases by more than 5 orders of magnitude when the RH decreases from 80 to 2%, following an S-shaped curve with small hysteresis. Moreover, the biased surfaces store charge, as shown by Kelvin potential measurements. Applying an electric field parallel to the surface produces RH-dependent results: under low humidity, the interface behaves as expected for an ideal two-dimensional parallel-plate capacitor, while under high RH, it acquires and maintains excess negative charge, which is lost under low RH. The glass surface morphology and potential distribution change on the glass/air interface under high RH and applied potential, including the extensive elimination of nonglass contaminating particles and potential levelling. All these surprising results are explained by using a protonic-charge-transfer mechanism: mobile protons dissociated from silanol groups migrate rapidly along a field-oriented adsorbed water layer, while the matrix-bound silicate anions remain immobile. Glass may thus be classified as the ionic analogue of a topological insulator but based on structural features and charge-transfer mechanisms different from the chalcogenides that have been receiving great attention in the literature. (AU)

• Processo FAPESP: 14/50906-9 - INCT 2014: em Materiais Complexos Funcionais (INOMAT)
• Beneficiário: Fernando Galembeck
• Modalidade de apoio: Auxílio à Pesquisa - Temático