Cross-section transmission electron microscopy of the ion implantation damage in annealed diamond

[摘要] Diamond with its outstanding and unique physical properties offers the opportunityto be used as semiconductor material in future device technologies. Promising ap-plications are, among others, high speed and high-power electronic devices workingunder extreme conditions, such as high temperature and harsh chemical environments.With respect to electronic applications, a controlled doping of the material is neces-sary which is preferably done by ion implantation. The ion implantation techniqueallows incorporation of foreign atoms at de¯ned depths and with controlled spatialdistribution which is not achievable with other methods. However, the ion implanta-tion process is always connected with the formation of defects which compensate andtrap charge carriers thus degrading the electrical behaviour. It is therefore essentialto understand the nature of defects produced under various implantation conditions.In this respect, this study involves the investigation of the nature of the radiationdamage produced during the multi-implantation of carbon ions in synthetic high-pressure, high-temperature (HPHT) type Ib diamond spread over a range of energiesfrom 50 to 150 keV and °uences, using the cold-implantation-rapid-annealing (CIRA)routine. Single energy implantation of carbon ions in synthetic HPHT (type Ib), atroom temperature, was also performed. Both ion milling and FIB (Focused IonBeam) milling were used to prepare thin specimen for transmission electron micro-scope (TEM) analysis.The unimplanted, implanted and annealed samples were characterized using trans-mission electron microscopy based techniques and Raman spectroscopy.iiiiiIn unimplanted type Ia natural diamond, a high density of platelets, exhibiting thetypical contrast of both edge-on and inclined platelets on f100g planes was found.As-implanted HPHT type Ib diamond, implanted with single energy of 150 keV car-bon ions and °uence of 7£1015 ions cm¡2 revealed an amorphous diamond layer ofabout 80 nm in thickness while, for low °uence implantations, the damaged diamondretained its crystallinity after annealing at 1600 K. In addition, damaged diamondtransformed into disordered carbon comprising regions with bent (002) graphiticfringes and regions of amorphous carbon when high °uence, i.e., one above the amor-phization/graphitisation threshold were used followed by rapid thermal annealing at1600 K. Furthermore, the interface between the implanted and annealed layer andthe diamond substrate at the end of the range, showed diamond crystallites, inter-spersed between regions of amorphous carbon and partially graphitized carbon. Thisindicates that solid phase epitaxial recrystallization regrowth in diamond does notoccur.

[发布机构] University of the Witwatersrand