Ohmic contacts on diamond were fabricated using a Ti/Pt/Au metallization scheme and two transmission line model masks. The double mask system is used to isolate the Ti by surrounding it with Pt. Pt is expected to prevent Ti diffusion either to the contact surface or along the diamond surface during annealing. In this study we found that this system of masks was successful in preventing the Ti diffusion as revealed by Auger analysis on the diamond and contact surfaces. An Auger depth profile revealed that the Ti was confined to the diamond/contact interfacial region, and was most likely combined with Pt.Diamond is expected to be a good host material for electronic and optical devices under severe conditions, such as high temperature and strong irradiation environment, because of its large energy gap (5.5 eV).' In many semiconductor devices including diamond, the quality of ohmic contacts plays a vital role in determining device performance limitations. There is a need for a low contact resistance metallization scheme. Ti/Au metallization has been employed for the fabrication of ohmic contacts on diamond with reported specific contact resistances of the order of 1O Cl cm2.2 However, Ti was found to diffuse to the contact surface after the anneal step.The resistance of a contact with Ti on its surface is expected to be larger than without the Ti present because Ti oxidizes easily and forms titanium oxide, an insulator. This forms a large potential barrier at the interface with diamond, which is an impediment to the formation of ohmic contacts. In an attempt to decrease the contact resistance by eliminating the diffusion of Ti to the contact surface and its subsequent oxidation, we employed a Ti/Pt/Au tnlayer metaffization scheme on natural lib diamond.3 In this scheme, the Pt served successfully as a vertical barrier to Ti diffusion into the Au capping layer. However, the Ti was
Using transmission electron microscopy and energy dispersive x-ray spectroscopy analysis, the microstructure and composition of a YBa2Cu3O7−x/Y2O3/YBa2Cu3O7−x trilayer film deposited on MgO by off-axis sputtering at 670 °C and 100 mTorr was investigated. The YBa2Cu3O7−x layer in contact with the substrate was found to be mainly single phase. However, the top YBa2Cu3O7−x layer was embedded with 5–10 nm crystalline Y2O3 (yttria) particles, which disturbed the local microstructure. The top YBa2Cu3O7−x layer also had barium copper oxide particles covering its surface. The partial decomposition of the top YBa2Cu3O7−x layer may have been due to resputtering of the yttria layer which locally altered the deposition conditions. In particular, the oxygen pressure in the vicinity of the growing film may have increased due to sputtering of the yttria layer by plasma gas atoms and the sputtered target atoms. As a result, deposition occurred under conditions away from the thermodynamic stability line.
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