HIRIS

Diamond heteroepitaxy constitutes one of the remaining challenges for technological applications. The most promising results are nowadays obtained with iridium substrates. Although the use of this material for detector applications is just starting, a strong potential is foreseen. Nevertheless, an accurate knowledge of the mechanisms promoting heteroepitaxy is needed to further improve film crystalline quality. The aim of the HIRIS project (Heteroepitaxial DIamond on iRIdium for DoSimetry) is to synthesize heteroepitaxial diamond film of very high crystalline quality on iridium buffer layers deposited on SrTiO3 (001) substrates and qualify them as radiotherapy dosimeters. HIRIS gathers three French groups leaders in the diamond community (CEA LIST, GEMaC, LSPM) having complementary expertises and the INL group which develop alternatives SrTiO3 / Si(001) substrates . The strength of the present consortium comes from the ability to control each step of the process, from the substrate preparation, going through diamond heteroepitaxial nucleation and growth and ending with the dosimeter design and test. Moreover, this approach is particularly innovative since no other running project aims at developing heteroepitaxial diamond for this particular application. The HIRIS project will be coordinated by CEA-LIST and organised as follows. At first, different alternative SrTiO3 / Si (001) substrates for iridium deposition will be grown by INL. The most promising one will be selected after 18 months. Heteroepitaxial diamond templates, a few microns thick, will be elaborated at CEA LIST using the Bias Enhanced Nucleation technique in a unique experimental set-up equipped with in situ accurate surface diagnoses, thus allowing studying the nucleation mechanisms of diamond. Specific PACVD conditions adapted to the growth of high crystalline quality diamond with a low impurity level will be then applied by LSPM to achieve thick free-standing heteroepitaxial (001) diamond films with a thickness up to 300 ?m. Diamond films will be studied after each step of their growth using extended surface, structural and chemical characterisations especially at GEMaC. Two of these heteroepitaxial diamond films will be finally tested as dosimeters (5 x 5 mm2) during the third year of the HIRIS project at CEA LIST. It is expected that the high quality heteroepitaxial (001) thick diamond crystals obtained will be reliable and efficient for dosimetry measurements. The up-scaling to larger dimensions (20 x 20 mm2) will also be investigated so as to explore the full potential of the process and have a wider impact on the diamond community. It will also provide after cutting a set of reproducible samples (5 x 5 mm2) for dosimetry. The results obtained by the members of the consortium will be reported in peer-reviewed journals and conferences. A particular attention will be paid to their protection. No publication will be made without agreement of all partners and prior search for patentability as it will be stated in the consortium agreement.