Showing papers by "Mildred S. Dresselhaus published in 1992"
TL;DR: In this paper, the electronic structure for graphenemonolayer tubules is predicted as a function of the diameter and helicity of the constituent graphene tubules, and it is shown that approximately 1/3 of these tubules are a one-dimensional metal which is stable against a Peierls distortion, and the other 2/3 are onedimensional semiconductors.
Abstract: The electronic structure for graphenemonolayer tubules is predicted as a function of the diameter and helicity of the constituent graphene tubules. The calculated results show that approximately 1/3 of these tubules are a one‐dimensional metal which is stable against a Peierls distortion, and the other 2/3 are one‐dimensional semiconductors. The implications of these results are discussed.
2,405 citations
TL;DR: A simple tight-binding model shows that some fibers are metallic and are stable against perturbations of the one-dimensional energy bands and the mixing of σ and π bands due to the curvature of the circumference of the fiber.
Abstract: The electronic structures of some possible carbon fibers nucleated from the hemisphere of a ${\mathrm{C}}_{60}$ molecule are presented. A one-dimensional electronic band-structure model of such carbon fibers, having not only rotational symmetry but also screw axes, is derived by folding the two-dimensional energy bands of graphite. A simple tight-binding model shows that some fibers are metallic and are stable against perturbations of the one-dimensional energy bands and the mixing of \ensuremath{\sigma} and \ensuremath{\pi} bands due to the curvature of the circumference of the fiber.
1,168 citations
Book•
01 Aug 1992
TL;DR: In this paper, the authors present a detailed analysis of the properties of graphite-based graphite and diamond-like carbon films, including the following properties: 1.1.1 Lattice properties, 2.2.3 Optical properties, 3.3.4 Thermal properties, 4.4 Energy Loss, 5.5 Electronic Transport Measurements, 6.5 Modification of Mechanical Properties, 7.6 Implantation-Enhanced Intercalation, 8.7.
Abstract: 1. Introduction.- 2. Carbon Materials: Graphite, Diamond and Others.- 2.1 Structure and Materials.- 2.1.1 Graphite.- 2.1.2 Graphite-Related Materials.- 2.1.3 Carbon Fibers.- 2.1.4 Glassy Carbon.- 2.1.5 Graphite Intercalation Compounds.- 2.1.6 Diamond.- 2.1.7 CVD Diamond Films.- 2.1.8 Diamond-Like Carbon Films.- 2.2 Properties of Graphite.- 2.2.1 Lattice Properties.- 2.2.2 Electronic and Transport Properties.- 2.2.3 Optical Properties.- 2.2.4 Thermal Properties.- 2.2.5 Mechanical Properties.- 2.3 Properties of Diamond.- 2.3.1 Lattice Properties.- 2.3.2 Electronic and Transport Properties.- 2.3.3 Optical Properties.- 2.3.4 Thermal Properties.- 2.3.5 Mechanical Properties.- 2.3.6 Chemical Properties.- 3. Ion Implantation.- 3.1 Energy Loss Mechanisms.- 3.2 Parameters of Implantation.- 3.2.1 Energy of Implantation.- 3.2.2 Implantation Range.- 3.2.3 Implantation Fluence (Dose) and Beam Current (Dose Rate).- 3.3 Radiation Damage.- 3.4 Energy Loss Simulations.- 4. Ion Beam Analysis Techniques.- 4.1 Rutherford Backscattering Spectroscopy.- 4.2 Nuclear Reaction Analysis.- 4.3 Particle Induced X-Ray Emission (PIXE).- 4.4 Channeling.- 4.5 Elastic Recoil Detection (ERD).- 4.6 Secondary Ion Mass Spectroscopy (SIMS).- 4.7 Channeling Studies in Graphite-Based Materials.- 4.8 Stoichiometric Characterization of GICs by RBS.- 4.9 Ion Channeling in GICs.- 5. Other Characterization Techniques.- 5.1 Raman Spectroscopy.- 5.2 Other Optical and Magneto-Optical Techniques.- 5.3 Electron Microscopies and Spectroscopies.- 5.4 X-Ray-Related Characterization Techniques.- 5.5 Electronic Transport Measurements.- 5.6 Electron Spin Resonance (ESR).- 5.7 Hyperfine Interactions.- 5.7.1 Mossbauer Spectroscopy.- 5.7.2 Perturbed Angular Correlations (PAC).- 5.8 Mechanical Properties.- 6. Implantation-Induced Modifications to Graphite.- 6.1 Lattice Damage.- 6.2 Regrowth of Ion-Implanted Graphite.- 6.3 Structural Modification.- 6.4 Modification of the Electronic Structure and Transport Properties.- 6.5 Modification of Mechanical Properties.- 6.6 Implantation with Ferromagnetic Ions.- 6.7 Implantation-Enhanced Intercalation.- 6.8 Implantation with Hydrogen and Deuterium.- 7. Implantation-Induced Modifications to Graphite-Related Materials.- 7.1 Glassy Carbon.- 7.2 Carbon Fibers.- 7.3 Disordered Graphite.- 7.4 Carbon-Based Polymers.- 8. Implantation-Induced Modifications to Diamond.- 8.1 Structural Modifications and Damage-Related Electrical Conductivity.- 8.2 Volume Expansion.- 8.3 Lattice Damage.- 8.4 Damage Annealing and Implantations at Elevated Temperatures.- 8.5 Electrical Doping.- 8.6 Impurity State Identification.- 8.7 Electronic Device Realization.- 8.8 New Materials Synthesis.- 8.9 Improving Mechanical Properties.- 9. Implantation-Induced Modifications to Diamond-Related Materials.- 9.1 Diamond-Like Carbon (a-C:H) Films.- 9.1.1 DC Conductivity.- 9.1.2 Optical Characterization.- 9.1.3 Structural Modifications and Hydrogen Loss.- 9.1.4 Attempts to Dope a-C:H by Ion-Implantation.- 9.1.5 Discussion of Implantation-Induced Effects in DLC.- 9.2 Diamond Films.- 10. Concluding Remarks.- References.
183 citations
TL;DR: In this paper, it is proposed that it may be possible to increase the thermoelectric figure of merit of certain materials by preparing them in quantum well superlattice structures.
Abstract: Currently the materials with the highest thermoelectric figure of merit, Z, are Bi2Te3 alloys. Therefore these compounds are the best thermoelectric refrigeration elements. However, since the 1960's only slow progress has been made in enhancing Z, either in Bi2Te3 alloys or in other thermoelectric materials. So far, the materials used in applications have all been in bulk form. In this paper, it is proposed that it may be possible to increase Z of certain materials by preparing them in quantum well superlattice structures. Calculations have been done to investigate the potential for such an approach, and also to evaluate the effect of anisotropy on the figure of merit. The calculations show that layering has the potential to increase significantly the figure of merit of a highly anisotropic material like Bi2Te3, provided that the superlattice multilayers are made in a particular orientation. This result opens the possibility of using quantum well superlattice structures to enhance the performance of thermoelectric coolers.
126 citations
TL;DR: In this paper, a topological defect consisting of a five and a seven-membered ring pair in a honeycomb lattice is proposed, and the defect pair can move smoothly in a hexagonal lattice during a bond change reaction without annihilation into two six-memered rings, until it collides with another pentagon defect.
105 citations
01 Jan 1992
TL;DR: In this article, the structure and magnetic properties of magnetic acceptor and donor graphite intercalation compounds (GICs) are reviewed and compared with recent evidence for 2D magnetism in acceptor GICs.
Abstract: Magnetic graphite intercalation compounds are layered magnetic materials in which the ratio of the intraplanar to interplanar exchange coupling can be varied by several orders of magnitude through intercalation and staging. In this chapter, the structure and magnetic properties of magnetic acceptor and donor graphite intercalation compounds (GICs) are reviewed. The relation between the GIC and the pristine intercalate makes it possible to measure the effect of staging in the GIC, including the crossover to lower dimensionality. The theory of two-dimensional (2D) magnetism is reviewed and compared with recent evidence for 2D magnetism in acceptor graphite intercalation compounds. The transition-metal dichloride acceptor compounds show larger magnetic anisotropies than the donor GICs and provide instructive examples of quasi-2D magnetic systems. The prototype 2D-XY system is the CoCl2 GIC, for which a large body of experimental data is presented to infer the 2D behavior. Experimental results for the commensurate stage-1 donor compound C6Eu are presented as an example of an anisotropic RKKY magnetic interaction. In addition, progress in the study of many magnetic acceptor GICs is reviewed.
6 citations
TL;DR: The hole carriers were found to have high mobilities, comparable to the mobilities of the graphitic ~ electrons, and the scattering mechanism for the ~ bands can be explained in terms of an acoustic-phonon scattering process with small effective masses and a large deformation potential.
Abstract: The Hall effect and magnetoresistance were measured for stage-1 and -2 potassium-hydrogen-graphite ternary intercalation compounds (KH-GIC's) in the temperature range 1.4--250 K, in order to investigate their electronic structure and transport properties. The presence of two kinds of carriers was found: majority carriers in the graphitic ${\mathrm{\ensuremath{\pi}}}^{\mathrm{*}}$ bands with electron character and minority hole carriers in the free-electron-like hydrogen 1s band. The hole carriers in the H 1s band are associated with the incomplete charge transfer to the hydrogen species. The Hall coefficient ${\mathit{R}}_{\mathit{H}}$ and conductivity tensor ${\mathrm{\ensuremath{\sigma}}}_{\mathit{x}\mathit{y}}$ component exhibit large temperature dependences, which are considered to be due to the different in-plane scattering mechanisms for the two kinds of carriers. The hole carriers were found to have high mobilities, comparable to the mobilities of the graphitic \ensuremath{\pi} electrons. The scattering mechanism for the ${\mathrm{\ensuremath{\pi}}}^{\mathrm{*}}$ bands can be explained in terms of an acoustic-phonon scattering process with small effective masses and a large deformation potential. On the other hand, that for the H 1s band is dominated by an acoustic-phonon scattering process, with a small deformation potential in the ionic ${\mathrm{K}}^{+}$${\mathrm{H}}^{\mathrm{\ensuremath{-}}}$ intercalate layers below 80 K, in addition to a low-energy optical-phonon scattering, which is operative mainly at higher temperatures.
4 citations