We present measurement results for the gradient of the Casimir force between an Au-coated sphere and an Au-coated plate obtained by means of an atomic force microscope operated in a frequency shift technique. This experiment was performed at a pressure of 3 × 10 −8 Torr with hollow glass sphere of 41.3 µm radius. Special attention is paid to electrostatic calibrations including the problem of electrostatic patches. All calibration parameters are shown to be separationindependent after the corrections for mechanical drift are included. The gradient of the Casimir force was measured in two ways with applied compensating voltage to the plate and with different applied voltages and subsequent subtraction of electric forces. The obtained mean gradients are shown to be in mutual agreement and in agreement with previous experiments performed using a micromachined oscillator. The obtained data are compared with theoretical predictions of the Lifshitz theory including corrections beyond the proximity force approximation. An independent comparison with no fitting parameters demonstrated that the Drude model approach is excluded by the data at a 67% confidence level over the separation region from 235 to 420 nm. The theoretical approach using the generalized plasma-like model is shown to be consistent with the data over the entire measurement range. Corrections due to the nonlinearity of oscillator are calculated and the application region of the linear regime is determined. A conclusion is made that the results of several performed experiments call for a thorough analysis of the basics of the theory of dispersion forces.

We present complete results of the experiment on measuring the Casimir force between an Aucoated 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 UVtreated samples are presented. The random, systematic and total experimental errors are determined at a 95% confidence level. It is demonstrated that the UV treatment of an ITO 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 in the dielectric permittivity. According to the hypothetical 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.

Additional information is provided on the effect of the significant (up to 35%) reduction in the magnitude of the Casimir force between an Au -coated sphere and an indium tin oxide film which was observed after UV treatment of the latter. A striking feature of this effect is that the reduction is not accompanied with a corresponding variation of the dielectric permittivity, as confirmed by direct ellipsometry measurements. The measurement data are compared with computations using the Lifshitz theory. It is shown that the data for the untreated sample are in a very good agreement with theory taking into account the free charge carriers in the indium tin oxide. The data for the UV-treated sample exclude the theoretical results obtained with account of free charge carriers. These data are found to be in a very good agreement with theory disregarding the free charge carriers in an indium tin oxide film. A possible theoretical explanation of our observations as a result of phase transition of indium tin oxide from metallic to dielectric state is discussed in comparison with other related experiments.

We propose two experiments on the measurement of the Casimir force acting between a gold coated sphere and semiconductor plates with markedly different charge carrier densities. In the first of these experiments a patterned Si plate is used which consists of two sections of different dopant densities and oscillates in the horizontal direction below a sphere. The measurement scheme in this experiment is differential, i.e., it allows the direct high-precision measurement of the difference of the Casimir forces between the sphere and sections of the patterned plate or the difference of the equivalent pressures between Au and patterned parallel plates with static and dynamic techniques, respectively. The second experiment proposes to measure the Casimir force between the same sphere and a VO 2 film which undergoes the insulator-metal phase transition with the increase of temperature. We report the present status of the interferometer based variable temperature apparatus developed to perform both experiments and present the first results on the calibration and sensitivity. The magnitudes of the Casimir forces and pressures in the experimental configurations are calculated using different theoretical approaches to the description of optical and conductivity properties of semiconductors at low frequencies proposed in the literature. It is shown that the suggested experiments will aid in the resolution of theoretical problems arising in the application of the Lifshitz theory at nonzero temperature to real materials.They will also open new opportunities in nanotechnology.

Abstract. Experimental methods and procedures required for precision measurements of the Casimir force are presented. In particular, the best practices for obtaining stable cantilevers, calibration of the cantilever, correction of thermal and mechanical drift, measuring the contact separation and the roughness are discussed. IntroductionThe role of the quantum vacuum and its modification by boundaries, generally referred to as the Casimir effect [1-6] is finding ever increasing applications in fields extending from cosmology to nanotechnology. In fundamental physics the Casimir force has been used for setting limits on the existence of extra dimensions and forces outside the standard model [7][8][9][10][11][12][13][14][15]. As the Casimir force dominates the interaction at separation distances less than 100 nm, its precision measurement is an effective probe of new physics at short distance scales. An interesting feature of the Casimir force is its strong material and geometry dependence. Theoretically the Casimir force can even be made repulsive through a judicious choice of materials [2,16] or boundary shape [3][4][5][6]. The significant role of the Casimir force has also been realized in nanotechnology, where operating surfaces in micromachines are separated by distances less than 1 micron [17,18]. Given the trend towards decreasing dimensions in nanotechnology, it is very conceivable that in the near future the distance scales will drop below 100nm. In this case, the Casimir force will have an overwhelming influence on both the design and function of microelectromechanical systems (MEMS).