Scientific and Technical Aerospace Reports Volume 39 April 6, 2001

the multiple sublattice molecular-field theory. by fitting theory to data, values are extracted for excited state energy splitting D
that enters the exponent (-D/kT) of the Orbach function.
Author
Ions; Rare Earth Elements; Spin-Lattice Relaxation; Temperature Dependence
20010025816 Midwest Superconductivity, Inc., Lawrence, KS USA
High current capacity high temperature superconducting film based tape for high field magnets Final Report
Xin, Y.; Jan. 01, 2000; 27p; In English
Report No.(s): DE00-758246; No Copyright; Avail: Department of Energy Information Bridge
The primary goal of the program was to establish the process parameters for the continuous deposition of high quality, superconducting
YBCO films on one meter lengths of buffered RABiTS tape using MOCVD and to characterize the potential utility
of the resulting tapes in high field magnet applications.
NTIS
Superconducting Films; YBCO Superconductors
20010026221 California Univ., Dept. of Physics, Riverside, CA USA
Etching Chemistry of III-V Semiconductors and the Development of Surface Roughness Final Report, Jul. 1995 - Jun.
1998
Yarmoff, Jory A.; Nov. 20, 2000; 6p; In English
Contract(s)/Grant(s): DAAH04-95-1-0290
Report No.(s): AD-A386178; ARO-34306.1-PH-AAS; No Copyright; Avail: CASI; A01, Microfiche; A02, Hardcopy
This research addressed the need for basic information concerning halogen etching of III-V semiconductors. The reactions
of halogens with semiconductor surfaces are the fundamental chemical interactions in processes employed for device manufacture.
In this work, the reactions of XeF2, CI2 and I2 with III-V semiconductor surfaces were investigated with synchrotron-based
soft x-ray photoelectron spectroscopy, low energy electron diffraction and scanning tunneling microscopy. Fluorine reaction
grows films of group III fluorides, which can be used as dielectric materials. Chlorine is the most widely used halogen for dry
etching. while iodine has been proposed for use as a ’gentle’& etchant. We found that, for all of the halogen reactions, the initial
adsorption depends on the surface reconstruction, stoichiometry and condition. Some surfaces passivate, while others spontaneously
etch at room temperature. The passivated surfaces are well-ordered and covered with approximately one monolayer of
adsorbed halogen. The etched surfaces, on the other and, are considerably rough and atomically disordered. A microscopic model
is proposed which assumes that halogen atoms preferentially adsorb onto a group III atom if the surface is initially well-ordered.
Further reaction depends on the ability of higher halides to form on the surface. This microscopic model can explain why certain
surfaces etch, while others form ordered overlayers.
DTIC
Etching; Semiconductors (Materials); Surface Roughness
20010026224 Air Force Research Lab., Propulsion Directorate West, Edwards AFB, CA USA
Crystal Structure of Hexamethylguanidinium Hexafluorosilicate Hexahydrate
Zhang, Xiongzhi; Bau, Robert; Sheehy, Jeffrey A.; Christe, Karl O.; Jan. 1998; 18p; In English
Report No.(s): AD-A386240; No Copyright; Avail: CASI; A01, Microfiche; A03, Hardcopy
Single crystals of the hexamethylguanidinium hexafluorosilicate hexahydrate salt, C(NMe2)32(+)SiF6(2-)(dot) 6H2O, were
isolated when a product, obtained by water removal from aqueous C(NMe2)3F in a glass vessel, was recrystallized from CH3OH.
The crystal structure of this salt was determined, and the structure of the free hexamethylguanidinium cation was calculated, showing
that the propeller-shaped structure of the hexamethylguanidinium cation is not caused by solid state effects but is the true minimum
energy structure.
DTIC
Crystal Structure; Methyl Alcohol; Single Crystals; Recrystallization; Silicates
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