Mark Hoinkis

Scandium clusters in fullerene cages.

The production and spectroscopic characterization of fullerene-encapsulated metal-atom clusters is reported. In particular, both solution and solid-state electron paramagnetic resonance (EPR) spectra of Sc3C82 have been obtained. ScC82 also gives an EPR spectrum, but Sc2Cn species—the most abundant metallofullerenes in the mass spectrum—are EPR-silent even though Sc2 is EPR-active in a rare-gas matrix at 4.2 K. The results suggest that the three scandium atoms in Sc3C82 form an equilateral triangle—as was previously suggested for Sc3 molecules isolated in a cryogenic rare-gas matrix. The spectrum of ScC82 has features similar to those found earlier for LaC82 and YC82, suggesting that it can also be described as a +3 metal cation within a -3 fullerene radical anion. An implication of this work is that production of macroscopic quantities of clustercontaining fullerenes may make possible the fabrication of exotic new structures with regular arrays of metal-atom clusters isolated in fullerene molecules, resulting in a new type of host/guest nanostructured material.

Multiple species of La@C82 and Y@C82. Mass spectroscopic and solution EPR studies

Abstract Two dominant electron paramagnetic resonance (EPR) hyperfine patterns for both La and Y fullerenes have been identified and linked to the mass spectroscopic (MS) peaks of La@C 82 and Y@C 82 , respectively, as also observed by Suzuki. Additionally, lower intensity La@C n EPR multiplets are identified which have not, as yet, been correlated with specific MS peaks. The intensity ratios of the two dominant EPR multiplets depend on various parameters such as solvent and temperature, suggesting the species possess different chemical properties.

High performance and low power transistors integrated in 65nm bulk CMOS technology

This paper reports a cutting-edge 65nm CMOS technology featuring high performance and low power CMOS devices for both general and low power applications. Utilizing plasma nitrided gate oxide, off-set and slim spacers, advanced co-implants, NiSi and low temperature MOL process, well designed NMOSFET and PMOSFET achieved significant improvement from the previous generation, especially PMOSFET has demonstrated an astonishing 35 % performance enhancement from the previous technology node

Characterization of fullerenes and doped fullerenes

Abstract The results of a variety of experiments used to characterize fullerenes, metallofullerenes and alkali-metal intercalated C 60 are reported. It is shown that differential scanning calorimetry and NMR characterization of the orientational phase transition in C 60 provide sensitive means to assess the purity and crystallinity of fullerene samples. The results of a mass-spectrometric investigation of metallofullerene samples produced by co-vaporization of carbon and metals are described. An account is given of some electron paramagnetic resonance results obtained for LaC 82 and solid-state NMR results obtained on an alkali-intercalated fullerite, Rb 3 C 60 , which show for the first time the presence of magnetically inequivalent carbons in underivatized C 60 . Together these experiments yield a great deal of information about the phase purity, molecular dynamics and structure of a variety of fullerene materials.

Solid-State NMR Studies of the Bonding Structure of Diamondlike Amorphous Carbon Films

Amorphous carbon films are (a-C:H) of interest because of their useful physical properties. They are extremely hard and chemically inert, resisting degradation by both acids and alkalis. They are insoluble and can be conformably coated onto virtually any substrate. These properties make the films ideal protective coatings on magnetic disks and tools. We have studied several thin (one to two micron) films prepared by plasma enhanced chemical vapor deposition with varying radiofrequency fields strengths to determine structural differences at the atomic level. Several properties of the films, such as hardness and wear rate, are dependent on deposition power. We have found that the sp 2 /sp 3 ratio increases with increasing deposition power. Thus, films that are harder are more “graphitic” and less “diamondlike”. The films studied here contain 11–16 atomic percent hydrogen, most of which is associated with sp 3 carbon sites. At least two distinct phases of hydrogens exist. Variable temperature studies reveal that, in contrast to amorphous hydrogenated silicon, proton linewidths in carbon films are temperature dependent, suggesting some molecular motion is present at room temperature.

Metal atoms and clusters in fullerene cages

Fullerenes containing metal atoms and clusters can be formed by the arc-vaporization method. The electronic structure of these metallofullerenes can be probed using magnetic resonance techniques. Electron paramagnetic resonance (EPR) spectra of LaC82, YC82, ScC82 and Sc3C82 have been obtained. Metallofullerenes containing a single metal atom (MC82 with M = La, Y, or Sc), have small hyperfine couplings and g-values close to 2, implying that they can be described as + 3 metal cations within — 3 fullerene radical anion cages. In the La and Y cases, additional EPR active MC82 species have been found. The EPR spectrum of Sc3C82 shows that the metal atoms are equivalent, suggesting that they may form a triangular molecule. No EPR spectrum is found for Y2C82 or for Sc2C2n species (with 2n = 82,84,86), suggesting that they are diamagnetic. Sc NMR spectra of a solution containing Sc2C2n species have been obtained which confirm the diamagnetism of the discandium metallofullerenes.