Impedance Study of GaN and InGaN Semiconductor Anion Selective Electrodes

Abstract

The response of potentiometric anion selective electrodes employing undoped GaN or In 0.2 Ga 0.8 N films as sensing element to detect various anions was investigated in solutions of KF, KNO 3 , KCl, HOC 6 H 4 COONa, KSCN, CH 3 COOK, KClO 4 and KBr salts. The calibration plots for the GaN and In 0.2 Ga 0.8 N semiconductor electrodes contained linear regions extending over four decades of activity change in most solutions. The structure of the GaN and In 0.2 Ga 0.8 N semiconductor electrode/ electrolyte interface was studied through electrochemical impedance spectroscopy. Analogous equivalent circuits modeling the GaN or In 0.2 Ga 0.8 N electrode/electrolyte interface were proposed and their parameters were calculated. The space charge layer of the GaN and In 0.2 Ga 0.8 N semiconductors dominated the impedance of the electrochemical system at high frequencies (> 10 kHz), whereas at low frequencies (< 10 kHz), the impedance was controlled by the diffusion of electroactive species across the layer of adsorbed ions at the surface of the electrode. Results imply a strong dependence of the electrodes performance on the adsorption capacity of tested anions.

ZnO nanorod/GaN light-emitting diodes: The origin of yellow and violet emission bands under reverse and forward bias

“…The carrier/acceptor concentration in the samples was provided by the supplier of the samples and verified by electrochemical impedance spectroscopy (EIS) measurements. [34][35][36] EIS was used as a technique capable of providing information for carrier concentration for both nanorods 34 and thin films, 35 unlike Hall measurements which could be used only for thin films. EIS was performed in a three-electrode cell.…”

“…The electrolyte used was carbonate propylene (0.1 M LiClO 4 ) and 0.1 M KCl for ZnO and p-GaN, respectively. 34,35 All EIS data were obtained using CH Instruments electrochemical workstation and the analysis was done by commercial software from CH Instruments. For ZnO, 20 mV sinusoidal signal was applied with constant dc bias, with frequency ranging from 500 kHz and 5 mHz.…”

“…34 For p-GaN, ac sinusoidal signal with 10 mV amplitude with constant dc bias and frequency ranging from 100 Hz to 500 kHz was used, and before the start and during the experiment cell was purged with argon gas. 35 The equivalent circuit consisted of a series resistance R s and parallel connection of a capacitance and a constant phase element for ZnO, while for p-GaN equivalent circuit consisted of a series resistance R s and parallel connection of a capacitance and a constant phase element in series with parallel resistance R p . Carrier concentration was then determined by MottSchottky analysis.…”

“…Carrier concentration was determined by EIS. [34][35][36] Cathodoluminescence (CL) measurements were also performed using JEOL JSM-7001 F SEM equipped with a CL setup (Gatan, Mono CL). For PL measurements at room temperature and variable power, a HeCd laser (325 nm) was used as an excitation source and the spectra were collected using a PDA-512_USB (Control Development Inc) fiberoptic spectrometer.…”

Electrochemical oxidation of lignin at IrO2-based oxide electrodes

“…The electrochemical performance of the IrO 2 -based electrodes was characterized using cyclic voltammetry (CV), chronopotentiometry (CP) and electrochemical impedance spectroscopy (EIS). A three-electrode cell system and a Solartron analytical SI 1287 system coupled with a Solartron analytical 1252A frequency response analyzer were used [30]. The prepared IrO 2 -based electrodes were used as working electrodes.…”