Metallization of Semiconducting Diamond: Mo, Mo/Au and Mo/Ni/Au

Abstract

PblIc reporting burden 1Wr this collection of bIfornalelon is 401maled to avrage I hourf Per ANSPOM. APRI 2 1993 9 -07481 l')'J Approved for public release; distribution is unlimited. ABSTRACT (Awmun 200 waro)A processing technology has been developed to make ohmic contacts to naturally doped semiconducting diamond. The approach follows, as far as possible, conventional photolithographic techniques for metallization of semiconductors currently in use in the microelectronic industry.Ohmic contacts have been successfully made to naturally doped semiconducting diamond using evaporated thin films of molybdenum, molybdenum/gold, and molybenum/nickel/gold. The metal contacts form a tenacious bond with the diamond suibstrate after annealing. The time and the temperature of annealing also affects the type and the degree of conduction of the contacts.Characterization of the interface of the metal contacts to diamond using AFS, SIMS, BBS, XRD, SEM, and metallography clearly indicates that metal-carbide-precipitates nucleate and grow at the diamond/metal interface during annealing. It is concluded that the size and the areal density of the carbide precipitates at the interface are the principal factors that control the adhesion, and the mode and the degree of conductivity of the metal contacts.Sponsorship of this research by SDIO/JSI, ONR, and NOSC/JR is gratefully acknowledged. Published in

The decoding region of 16S RNA; a cross-linking study of the ribosomal A, P and E sites using tRNA derivatized at position 32 in the anticodon loop.

“…A further striking feature of the data is the degree of coincidence between the crosslink positions and P-site footprints, a phenomenon which has also been noted in the 23S RNA, with regard to cross-links from the aminoacyl moiety of tRNA (Steiner et al, 1988;Mitchell et al, 1993) and footprints from its 3'-terminus (Moazed and Noller, 1989). In addition to those cases just discussed, the P site cross-link at nucleotide 966 in helix 31 and the P and E site cross-links at nucleotide 693 in helix 23 ( Figure 5) are identical with P site footprint positions (Moazed and Noller, 1990); from the cross-link data, it can be concluded that the loop-ends of these two helices (23 and 31) are indeed directly involved in the decoding region. From similar cross-linking studies with mRNA, helices 18 and 34 (Dontsova et al, 1992) and now helix 22 (J.Rinke-Appel et al, in preparation) are also part of the same neighbourhood.…”

“…'P-34' indicates the site of cross-linldng to position 34 of P site bound tRNA (Prince et al, 1982). Solid triangles and circles denote sites of footprinting from A or P site bound tRNA, respectively (Moazed and Noller, 1990). Sites of cross-linking to ribosomal proteins S7, Sll, S13 and S19 are also included.…”

“…Taken together with the other data ( Figure 5), the cross-links provide a new insight into the topography of the decoding region of the 16S RNA and in particular indicate that the area surrounding helices 28, 29, 43 and 44 must be folded in an extremely convoluted fashion involving all three tRNA binding sites. Thus, beginning at the lower left-hand corner of Figure 5, there are A site tRNA footprint positions (Moazed and Noller, 1990) located at the upper end of helix 44. Nearby, at nucleotide 1402, there is a cross-link to position +4 within the A site codon of mRNA (Rinke-Appel et al, 1993), and immediately adjacent are the P site tRNA footprint positions (Moazed and Noller, 1990) and the cross-link from position 34 of P site tRNA to nucleotide C-1400 (Prince et al, 1982).…”

“…Thus, beginning at the lower left-hand corner of Figure 5, there are A site tRNA footprint positions (Moazed and Noller, 1990) located at the upper end of helix 44. Nearby, at nucleotide 1402, there is a cross-link to position +4 within the A site codon of mRNA (Rinke-Appel et al, 1993), and immediately adjacent are the P site tRNA footprint positions (Moazed and Noller, 1990) and the cross-link from position 34 of P site tRNA to nucleotide C-1400 (Prince et al, 1982). Next, at nucleotide 1395 is the cross-link to position +7 of the mRNA, just downstream of the A site codon (Dontsova et al, 1992), which is in turn close to a P site footprint at nucleotide 926 in helix 28.…”

“…Next, at nucleotide 1395 is the cross-link to position +7 of the mRNA, just downstream of the A site codon (Dontsova et al, 1992), which is in turn close to a P site footprint at nucleotide 926 in helix 28. The single-stranded 'ring' connecting helices 28, 29 and 43 contains both of the tRNAArgI A site cross-links (Table I), as well as the E site cross-link at nucleotides 1376-1378 and another P site footprint at nucleotide 1381 (Moazed and Noller, 1990). The P site cross-link at nucleotide 1338 (Table I) adjacent to helix 29 coincides with a P site footprint at the same position.…”