Integrated Diamond Film Microcircuit For High-pressure Electrical Resistivity Measurement

Diamond anvil cell is the most powerful tool for generating ultrahigh pressure. Combined with many other measurements it could be used for many in-situ measurements at high temperature and high pressure. A fantastic development has been appeared on the research of high pressure properties of materials with the development and application of the DAC technique. People may obtain the information on materials, such as structural phase transitions,electronic correlation,lattice vibration et al at extreme conditions. Thus far many in-situ measurements have been conducted on DAC, such as structure,spectroscopy,light emission,light scattering and so on. However, as one of most important aspects for matter property research, it has been reported less for technique restriction. Up to now, the experiment technique of resistance measurement concerning corrosive sample in DAC has not been reported because of the damageability of metal electrodes.Base on the film deposition technique, we devised a novel approach of integrating B doped diamond films on DAC surface. We have been succeeded in preparation and characterization of this electrode. We have measured the conductivity of water at pressure from ambient pressure to 2.7 GPa, and a series of important information have been obtained. Electrical resistivity measurement is based on the Van der Pauw method, and the average resistance of the four electrodes is 180?. We found the electrodes were not damaged after downloading, which proved its practicability.We used photolithographic method and selective seeding with nano diamond powers technique in integrating the diamond film microcircuit. We also used selective seeding with diamond powder technique in diamond deposition onto alumina substrate, and we successfully prepared diamond film/alumina composites. We characterized the electrodes and the composites using SEM,XRD and Raman spectroscopy, and some useful information on diamond deposition seeding with diamond powder was obtained, as follows:1. The substrates were not damaged during the whole process.2. Compared with the method of abrading substrates, it needs lower nucleation temperature.3. The time of film deposition is observably shorter than that of method of abrading substrates.4. We could prepared patterned diamond film/alumina composite by this method.5. The defects, grain boundary provided by nano powders facilitate Boron doping.In a LHDAC system, heat insulation plays an important role. Bulk diamond has the highest thermal conductivity in the known materials, which transmits a large amount of heat away from the sample. It thus prevents the sample from reaching high temperatures. With a diamond film/alumina composites film acting as thermal insulation layer, we presented a novel design of diamond anvil cell for in situ HPHT resistance measurement. We believe, the diamond film/alumina composites film is an effective thermal insulation layer for its lower conductivity and corrosion proof.