Modifying the Casimir force between indium tin oxide film and Au sphere

TL;DR

This study measures the Casimir force between an Au sphere and indium tin oxide (ITO) films, showing UV treatment significantly reduces the force without changing dielectric properties, indicating a phase transition affecting free charge carriers.

Contribution

The paper demonstrates how UV treatment induces a phase transition in ITO films, altering the Casimir force and providing insights into material behavior relevant for nanotechnology applications.

Findings

UV treatment reduces Casimir force by 21-35%.

Dielectric permittivity remains unchanged after UV treatment.

Data supports phase transition from metallic to dielectric state.

Abstract

We present complete results of the experiment on measuring the Casimir force between an Au-coated sphere and an untreated or, alternatively, UV-treated indium tin oxide film deposited on a quartz substrate. Measurements were performed using an atomic force microscope in a high vacuum chamber. The measurement system was calibrated electrostatically. Special analysis of the systematic deviations is performed, and respective corrections in the calibration parameters are introduced. The corrected parameters are free from anomalies discussed in the literature. The experimental data for the Casimir force from two measurement sets for both untreated and UV-treated samples are presented. The experimental errors are determined at a 95% confidence level. It is demonstrated that the UV treatment of an I TO plate results in a significant decrease in the magnitude of the Casimir force (from 21% to 35% depending on separation). However, ellipsometry measurements of the imaginary parts of dielectric permittivities of the untreated and UV-treated samples did not reveal any significant differences. The experimental data are compared with computations in the framework of the Lifshitz theory. It is found that the data for the untreated sample are in a very good agreement with theoretical results taking into account the free charge carriers in an ITO film. For the UV-treated sample the data exclude the theoretical results obtained with account of free charge carriers. These data are in a very good agreement with computations disregarding the contribution of free carriers. According to the explanation provided, this is caused by the phase transition of the ITO film from metallic to dielectric state caused by the UV treatment. Possible applications of the discovered phenomenon in nanotechnology are discussed.