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Metal-Electrolyte-Semiconductor Capacitors to Quantify Interface State Density in Printed ZnO for Low-Voltage UV Photodetectors

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Author(s):
Vieira, Douglas Henrique ; Nogueira, Gabriel Leonardo ; de Oliveira, Rafael Furlan ; Gomes, Henrique Leonel ; Alves, Neri
Total Authors: 5
Document type: Journal article
Source: ACS APPLIED ELECTRONIC MATERIALS; v. 7, n. 17, p. 11-pg., 2025-08-28.
Abstract

This study reports the fabrication and electrical characterization of metal-electrolyte-semiconductor (MES) capacitors based on printed ZnO as a semiconducting layer and a cellulose-based eco-friendly electrolyte. The results demonstrate that MES capacitors behave similarly to their solid-state metal-insulator-semiconductor (MIS) counterparts. Capacitance-voltage measurements show well-defined charge saturation and depletion plateaus, and the Mott-Schottky plots exhibit the expected linear behavior, allowing the extraction of the semiconductor free carrier density. Upon UV light exposure with varying irradiance, the flat-band voltage shifts consistently with a light-induced increase in free carrier density, and the capacitance increases due to trap filling. These behaviors are confirmed by measurements using a phototransistor structure. The frequency response of the MES capacitors also reveals low-frequency relaxation peaks in the capacitance spectrum, which align with a continuous distribution of interface state density reaching approximately similar to 4.86 x 1013 cm-2<middle dot>eV-1. These findings confirm that MES capacitors can effectively quantify electronic states at the electrolyte/semiconductor interface. This capability, along with a high capacitance ratio [C light - C dark]/C dark at very low voltages, is particularly valuable for applying MES devices in a wide range of sensing applications, especially in field-effect photodetectors. (AU)

FAPESP's process: 20/12282-4 - Development of vertical electrolyte-gated field effect transistors for UV photodetectors
Grantee:Douglas Henrique Vieira
Support Opportunities: Scholarships in Brazil - Doctorate
FAPESP's process: 21/06238-5 - Functionalized solution-processed 2D materials: development of prototyping electric sensors and biosensors
Grantee:Rafael Furlan de Oliveira
Support Opportunities: Research Grants - Young Investigators Grants