Mott-Schottky Analysis

Significance of the Topic

Using Mott–Schottky analysis via electrochemical impedance spectroscopy (EIS) to characterize semiconducting materials is essential for optimizing electronic and photoelectrochemical devices involved in energy conversion and storage. This technique offers non-destructive, rapid access to key parameters such as doping density and flatband potential.

Study Objectives and Overview

This study demonstrates a Mott–Schottky measurement on fluorine-doped tin oxide (FTO) using a VIONIC potentiostat powered by INTELLO software. It aims to extract the flatband potential and carrier concentration of the FTO electrode immersed in a neutral electrolyte.

Methodology

The procedure involved:

• Initial EIS at 0 V (100 kHz–0.1 Hz) to determine uncompensated resistance (R_s).
• Sequential impedance measurements at 1 kHz across DC offsets from 0 V to 1 V in 0.1 V increments.
• Calculation of space-charge capacitance from the imaginary impedance component using –Z″/ω.
• Construction of a Mott–Schottky plot (1/C² vs. applied potential) to derive electronic parameters via linear regression.

Applied Instrumentation

• Potentiostat/Galvanostat: VIONIC powered by INTELLO
• Analysis Software: NOVA
• Cell: 250 mL three-electrode configuration
• Working Electrode: FTO-coated glass slide (25 × 25 × 1 mm)
• Counter Electrode: Two platinum sheets in parallel
• Reference Electrode: Ag/AgCl (3 M NaCl)
• Electrolyte: 0.1 M NaCl, ambient atmosphere

Main Results and Discussion

• Uncompensated resistance (R_s) found to be 29.9 Ω via Nyquist fitting to an R–R/C equivalent circuit.
• The Mott–Schottky plot exhibited a positive slope, confirming n-type conductivity of FTO.
• Flatband potential (E_FB) determined as −1.61 V vs. Ag/AgCl (3 M) (−1.40 V vs. SHE).
• Doping density (N_D) calculated at 2.90 × 10²¹ cm⁻³ using ε = 2.137.
• All values align with literature benchmarks for FTO.

Benefits and Practical Applications

• Provides quick, non-destructive evaluation of semiconductor properties.
• Requires only standard EIS instrumentation with minimal specialized hardware.
• Suitable for screening materials in photovoltaics, sensors, and photocatalysis.

Future Trends and Opportunities

• Integration of operando EIS for real-time monitoring of dynamic processes.
• Extension to higher-frequency EIS to resolve fast interfacial phenomena.
• Automation and AI-assisted data analysis for high-throughput material discovery.
• Combination with complementary surface- and bulk-sensitive techniques for holistic material characterization.

Conclusion

Mott–Schottky analysis using VIONIC/INTELLO reliably extracts critical electronic parameters of FTO electrodes, matching established literature values and supporting its adoption in semiconductor research.

Reference

1. Korjenic A, Raja KS. Electrochemical Stability of Fluorine Doped Tin Oxide (FTO) Coating at Different pH Conditions. J Electrochem Soc. 2019;166(6):C169–C184.
2. Hankin A, Bedoya-Lora FE, Alexander JC, et al. Flat Band Potential Determination: Avoiding the Pitfalls. J Mater Chem A. 2019;7(45):26162–26176.
3. Sanz-Navarro CF, Lee SF, Yap SS, et al. Electrochemical Stability and Corrosion Mechanism of Fluorine-Doped Tin Oxide Film under Cathodic Polarization in Near Neutral Electrolyte. Thin Solid Films. 2023;768:139697.