Germanium(ll)phthalocyanine forms crystals belonging to space group P2/c with a=27.11, sigma=0.012 Å, b=10.39, sigma=0.020 Å, c=21.96, sigma=0.014 Å, beta=107.86, sigma-0.0680. There are eight molecules per unit cell.Patterson maps show that the molecule is planar, that the molecular axis is inclined 500 to the b axis, and that molecules are located parallel to each other along the b axis with an interplanar distance of 3.9 Å.

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Thesis (Ph. D.)--University of Texas at Austin, 2005. / Vita. Includes bibliographical references.

published_or_final_version / Physics / Master / Master of Philosophy

Thesis (M. Phil.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 91-92) Also available in print.

The surface chemistry of GeH[subscript x] with dielectric surfaces is relevant to the application of germanium (Ge) nanocrystals for nanocrystal flash memory devices. GeH[subscript x] surface chemistry was first explored for thermally-grown SiO₂ revealing that GeH[subscript x] undergoes two temperature dependent reactions that remove Ge from the SiO₂ surface as GeH₄ and Ge, respectively. Ge only accumulates due to reactions between GeH[subscript x] species that form stable Ge clusters on the SiO₂ surface. Next, a Si-etched SiO₂ surface is probed by GeH[subscript x] revealing that the Si-etching defect activates the surface toward Ge deposition. The activation involves two separate reactions involving, first, the capture of GeH[subscript x] by the defect and second, a reaction between the captured Ge and remaining GeH[subscript x] species leading to the formation of Ge clusters. Reacting the defect with diborane, deactivates it toward GeH[subscript x] and also deactivates intrinsic hydroxyl groups toward GeH[subscript x] adsorption. A structure is proposed for the Si-etching defect. The surface chemistry of GeHx with HfO₂ is studied showing that the hafnium germinate that forms beneath the Ge nanocrystals exists as islands and not a continuous film. Annealing the hafnium germinate under a silane atmosphere will reduce it to Ge while leading to the deposition of hafnium silicate (HfSiO[subscript x]) and silicon (Si). Treating the HfO₂ with silane prior to Ge nanocrystal growth yields a surface with hafnium silicate islands on which Si also deposits. Ge deposition on this surface leads to the suppression of hafnium germinate formation. Electrical testing of capacitors made from Ge nanocrystals and HfO₂ shows that Ge nanocrystals encapsulated in Si/HfSiO[subscript x] layers have greatly improved retention characteristics. / text

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This dissertation describes the development of a process for the precise positioning of semiconductor nanoparticles grown by hot wire chemical vapor deposition and thermal chemical vapor deposition on amorphous dielectrics, and it presents two studies that demonstrate the process. The studies entailed growth and characterization using surface science techniques and scanning electron microscopy. The two systems, Ge nanoparticles on HfO₂ and Si nanoparticles on Si₃N₄, are of interest because their electronic properties show potential in flash memory devices. The positioning technique resulted in nanoparticles deposited within 20 nm diameter feature arrays having a 6x10¹⁰ cm⁻² feature density. Self-assembling diblock copolymer poly(styrene-b-methyl methacrylate) thin films served as the patterning soft mask. The diblock copolymer features were transferred using a CHF₃/O₂ reactive ion etch chemistry into a thin film SiO₂ hard mask to expose the desired HfO₂ or Si₃N₄ deposition surface underneath. Selective deposition upon exposed pore bottoms was performed at conditions where adatom accumulation occurred on the HfO₂ or Si₃N₄ surfaces and not upon the SiO₂ mask template. The selective deposition temperatures for the Ge/HfO₂ and Si/Si₃N₄ systems were 700 to 800 K and 900 to 1025 K, respectively. Germanium nucleation on HfO₂ is limited from hot wire chemical vapor deposition by depositing nanoparticles within 67% of the available features. Unity filling of features with Ge nanoparticles was achieved using room temperature adatom seeding before deposition. Nanoparticle shape and size are regulated through the Ge interactions with the SiO₂ feature sidewalls with the adatom removal rate from the features being a function of temperature. The SiO₂ mask limited Ge nanoparticle growth laterally to within ~5 nm of the hard mask at 800 K. Silicon deposition on patterned Si₃N₄ has multiple nanoparticles, up to four, within individual 20 nm features resulting from the highly reactive Si₃N₄ deposition surface. Silicon nucleation and continued nanoparticle growth is a linear function of deposition flux and an inverse function of sample temperature. Diblock copolymer organization can be directed into continuous crystalline domains having ordered minority phases in a process known as graphoepitaxy. In graphoepitaxy forced alignment within microscopic features occurs provided certain dimensional constraints are satisfied. Graphoepitaxy was attempted to precisely locate 20 nm diameter features for selective Ge or Si deposition and initial studies are presented. In addition to precise nanoparticle positioning studies, kinetic studies were performed using the Ge/HfO₂ material system. Germanium hot wire chemical vapor deposition on unpatterned HfO₂ surfaces was interpreted within the mathematical framework of mean-field nucleation theory. A critical cluster size of zero and critical cluster activation energy of 0.4 to 0.6 eV were estimated. Restricting HfO₂ deposition area to a 200 nm to 100 [mu]m feature-width range using SiO₂ decreases nanoparticle density compared to unpatterned surfaces. The studies reveal the activation energies for surface diffusion, nucleation, and Ge etching of SiO₂ are similar in magnitude. Comparable activation energies for Ge desorption, surface diffusion and cluster formation obscure the change with temperature an individual process rate has on nanoparticle growth characteristics as the feature size changes. / text