Single Crystal Synthetic Diamond
Research and Development of Single Crystal Synthetic Diamond Technologies and Devices
Tech Area / Field
- MAT-SYN/Materials Synthesis and Processing/Materials
3 Approved without Funding
Institute of Physical-Technical Problems, Russia, Moscow reg., Dubna
- NPO Orion, Russia, Moscow
- Imperial College of Science, Technology and Medicine / Blackett Laboratory, UK, London\nLoma Londa University / Medical Center, USA, CA, Loma Linda
Project summaryDiamond is an ultimate limit in IV-group semiconductor series (Ge, Si, C) with the minimum atomic number and maximum crystal lattice binding energy. Therefore it is naturally unique material due to its outstanding properties. Relatively high radiation hardness and high temperature operation ability are the most attractive features for radiation detection applications. Low carbon nucleus charge (Z=6) provides tissue equivalence of diamond detectors. High carrier mobility (similar to that of Si) and thermal conductivity (5 times higher than copper one) put it to the most perspective materials for the future industrial technologies.
In spite of remarkable advances in artificial diamond films technology achieved last few years, the structural quality of CVD diamond samples could not be high enough to provide the quality required for the most attractive applications due to its native polycrystal structure. Up to now the best samples of natural diamond detectors (NDD) have about an order of magnitude better key parameters in comparison with the best artificial ones. Nevertheless, the main problem arising using NDD is the need to find natural diamonds of the IIa type with the required properties. Due to the fact that natural diamond coming from different miners never present the same characteristics, it is proved to be impossible in practice to produce batch of NDD with the same characteristics. Therefore the research and development of effective synthetic single crystal diamond (SD) growth methods providing improved level of intrinsic defects, impurities and other critical parameters, seem to be one of the most important directions of diamond technology activities. The problem of controllable single crystal diamond doping being solved, the event undoubtedly would be comparable with the transition between the basic semiconductors from Ge to Si in 60-s.
The development of such methods, studies of detector ultimate performance limiting factors, advance of synthetic single crystal diamond and natural diamond detector technologies are the main purposes of the Project. Realization of these purposes will be grounded on the experimental basis achieved by several Russian research teams which personnel will be mainly involved into the Project activities. As far as their previous occupations were related to nuclear weapons developments and other military applications (nuclear explosion metrology, anti-ballistic missile infrared aiming systems, etc.), - this work will provide peaceful alternative opportunities for the former Soviet weapon scientists and engineers.
The following applications seem to be the most promising for diamond synthetic single crystal technologies:
1. Solar sensors of unfavorable UV radiation increasing the imposed risk for skin solar burn and cancer diseases.
2. Radiation monitoring in the nuclear wastes burial-grounds and other critical zones of possible radioactive contamination leakage.
3. Dosimetry and spectrometry of X-ray, alpha, beta, gamma and neutron radiation for the purposes of medical radiotherapy, nuclear reactor control and other detectors for astronomy and space research applications.
4. Effective isolation heat sink thermoconductors with enhances electric hardness and extended temperature range for high power devices and components.
5. Wide band optical windows with enhanced mechanical, thermal and chemical hardness.
6. Components and devices for high voltage high temperature applications.
7. High radiation damage level detectors and electron components for nuclear power plants, plasma nuclear fusion and space astronomy applications.
Advanced synthetic single crystal diamond technologies for the wide range of UV, X-ray, gamma, neutron and other kind radiation detectors manufacturing would be the most perspective result of the project. These detectors could meet the demands in solar sensors of unfavorable UV radiation, nuclear wastes burial-ground dosimetry (at extremely high temperatures and radiation levels), medical microdosimetry. Also this work will provide the base for solving some problems of medicine, ecology and nuclear safety, study and characterization of nuclear fusion products at the future tokamak reactors.
Strategic perspective results could be foreseen also in other promising directions of synthetic diamond technology applications in future solid state electronics after the first basic methods of diamond electron structures will be developed.
In the framework of the Project it is planned to:
- advance the technology of high quality synthetic diamond single crystal growth;
- study of single crystal synthetic diamond optical and semiconductor properties;
- develop the diamond detector technologies for various ionizing radiation detection applications and other basic elements of solid state electronics;
- develop the detectors, probes, sensors and radiation intensity measuring devices for custom use, medical, ecology monitoring and nuclear diagnostics applications.
Technical approach to the Project fulfillment will be based upon the presently available results of scientific researches carried out last years by different teams in the former USSR, generally purposed to military applications. It will be accomplished by the joint team including the main part of their stuff. Further investigations of diamond electric properties are necessary for diamond technology modification for peaceful applications. Both already tested and newly developed research methods in conjunctive fields of science will be used.
The development of diamond synthesis technology providing the desired single crystal quality will be the general purpose at the first stage of work. Detailed physical analysis and experimental study of diamond band structure, charge carrier energy distributions, transport and transient processes in the crystal volume will be required. Raw materials and wafers classification criteria, improvements in selection and testing procedures ordered for high quality diamond detector manufacturing will be developed simultaneously.
On the next stage of work the investigations of synthetic diamond junction properties and corresponding technological experiments will be necessary. Detailed calculations of contact and the whole detector structure models will be carried out. This part of work will be closely related to developments, achievements and particular improvements in the detector manufacturing processes. Besides of the experimental research great attention will be paid to theoretical studies.
At the final stage most efforts will be applied to designing and manufacturing of various detectors, units and assemblies with required technical properties, their metrology, calibration and testing at real application environment conditions. A lot of work concerning the optimization of device configuration, electric circuits and final design could be foreseen. Further researches and developments in diamond technologies will be carried out also, if necessary.
It should be noted that the opportunity of SD testing at modern nuclear physical environments, definitely proved to be one of the most essential factors for the Project successful completion. The remarkable role of foreign collaborators should be emphasized for this reason and due to the absence of comparable operating environment in Russia. First of all it concerns the opportunities of researches at Blackett Lab., Imperial College (London UK), kindly given by Dr. J.Hassard, who provided strong support for the Project in EC owing to importance of radiation hard detectors. Loma Linda University Medical Center (Loma Linda, CA, USA) supported current Project as well.