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Papers by Andrew Chizmeshya

Molecular Engineering, 1996

Physical Review B, 1994

ABSTRACT

Physical Review B, 1988

... 15 FEBRUARY 1988-II Second-harmonic generation at metal surfaces using an extended Thomas —Fe... more ... 15 FEBRUARY 1988-II Second-harmonic generation at metal surfaces using an extended Thomas —Fermi-von Weizsacker theory ... Thomas-Fermi energy is capable of capturing an essen-tial part of the wave-mechanical behavior. ...

ChemInform, 1998

Bonding Trends in (NSF) 3 at High-Pressures.

MRS Proceedings, 1997

ABSTRACT

MRS Proceedings, 2002

Page 1. New Ge-Sn materials with adjustable bandgaps and lattice constants Matthew R. Bauer, 1 Jo... more Page 1. New Ge-Sn materials with adjustable bandgaps and lattice constants Matthew R. Bauer, 1 John Tolle, 1 AVG Chizmeshya, 2 S. Zollner, 3 J. Menendez, 4 and J. Kouvetakis 1 1 Department of Chemistry and Biochemistry ...

ChemInform, 2007

ABSTRACT We introduce a new chemical approach to the incorporation of high concentrations of acti... more ABSTRACT We introduce a new chemical approach to the incorporation of high concentrations of active n-dopant atoms into group-IV semiconductors via low temperature, low cost, high efficiency routes involving carbon-free single-source inorganic hydrides. Controlled substitution of As into Ge-based semiconductors is made possible by the use of As(GeH3)3, which furnishes structurally and chemically compatible AsGe3 molecular cores. As(GeH3)3 is synthesized in high purity yields (75%) via a new single-step method based on reactions of GeH3Br and As[Si(CH3)3]3, circumventing the need for toxic and unstable starting materials as used in earlier approaches. We demonstrate the development of a viable route to the entire family of compounds M(GeH3)3 {M = P, As, Sb}, suitable for doping or superdoping applications of a wide range of functional materials. The structural, vibrational, and thermochemical properties of M(GeH3)3 are simulated for the first time via density functional theory calculations using both all-electron and effective core potentials. The vibrational calculations are in excellent agreement with the observed infrared spectra and the thermochemical stability is predicted to decrease with increasing molecular mass, in accord with experimental observations. The simulated structures show that the Ge−M−Ge angles decrease with increasing M size and further resolve inconsistencies with earlier gas electron diffraction measurements of P(GeH3)3. Bulk supercell calculations are then used to study the formation free energy of P, As, and Sb incorporation in bulk Ge, as well as the bond and lattice strains induced by the dopant atoms in the host diamond-structure lattice. As a first example of the usability of the M(GeH3)3 family, we demonstrate the successful doping of metastable Ge1-ySny alloys. This represents a crucial step toward the goal of developing photonic devices, such as photodetectors and photovoltaic cells, based on Ge1-ySny. Infrared ellipsometry experiments demonstrate high carrier concentrations and excellent resistivities in As(GeH3)3-doped Ge1-ySny. The latter are only moderately higher than those measured in pure Ge for the same dopant levels.

Atomic and Molecular Beams, 2001

Surface Science Letters, 1989

ABSTRACT

MRS Proceedings, 2006

ABSTRACT Our experiences in research on nanoscience and technology using various microscopies to ... more ABSTRACT Our experiences in research on nanoscience and technology using various microscopies to observe materials synthesis reactions and to measure local (∼ 0.1-100 nm scale) structure and composition variations in solids provide some very useful examples to introduce students to important concepts of the field. The fundamental concept to illustrate is the nanometer length scale, of course, but other concepts such as mass and energy flows at the nanometer level and their effects on materials properties are at least as important, but more difficult to bring to students in a challenging but understandable way. We are using dynamic in situ or animated microscopy experiments in several material systems to teach these concepts. These experimental research results provide a useful basis for student computer modeling experiments, to give them direct participation in nanoscale materials research at an appropriate level. We are also exploring student group participation in live (interactive) electron microscopy experience via remote access into a suitably equipped computer visualization classroom.

Chemistry of Materials, 2014

IEEE Photonics Journal, 2010

We report new approaches based on rational design and preparation of chemical vapor deposition pr... more We report new approaches based on rational design and preparation of chemical vapor deposition precursors involving novel main-group hydrides to fabricate new families of Si-based semiconductors and prototype devices that display compositional and structural inheritance, from the parent molecule to the solid end product. This methodology enables materials synthesis at extraordinarily low temperatures that are compatible with complementary metal-oxide-semiconductor (CMOS) processing/selective growth and provides the means for obtaining highly metastable strain states in prototype structures that cannot be obtained by conventional protocols. Some of the materials and devices under development, involving alloys in the Si-Ge-Sn system, open up exciting opportunities in photodetectors and photovoltaics because they grow directly on cheap Si substrates and cover an extended range of the near-infrared spectrum that is not accessible to current photovoltaic and optoelectronic group IV semiconductors. impurities into the final product, thereby degrading device performance. On the other hand, the weakly bonded H ligands are readily eliminated as highly stable, noncorrosive H 2 , leaving groups leading to the highest possible purity in the final product at extraordinarily low temperatures that are well below the typical desorption range of H atoms in conventional CVD of semiconductors . Accordingly, the latter may serve as surfactants in the epitaxy-driven crystal assembly of materials possessing fundamentally incompatible surface energies. Our work to date provides mounting evidence that this metastable regime is responsible for the layer-by-layer growth of perfectly uniform and atomically flat heterostructures suitable for the development of thick device quality films. Most importantly, this low-temperature nontraditional processing is perfectly compatible with the fabrication of thermally sensitive device structures in typical back-end complementary metaloxide-semiconductor (CMOS) processes.

ChemInform, 2005

The synthesis of the entire silyl-germyl sequence of molecules (H(3)Ge)(x)SiH(4)(-)(x) (x = 1-4) ... more The synthesis of the entire silyl-germyl sequence of molecules (H(3)Ge)(x)SiH(4)(-)(x) (x = 1-4) has been demonstrated. These include the previously unknown (H(3)Ge)(2)SiH(2), (H(3)Ge)(3)SiH, and (H(3)Ge)(4)Si species as well as the H(3)GeSiH(3) analogue which is obtained in practical high-purity yields as a viable alternative to disilane and digermane for semiconductor applications. The molecules are characterized by FTIR, multinuclear NMR, mass spectrometry, and Rutherford backscattering. The structural, thermochemical, and vibrational properties are studied using density functional theory. A detailed comparison of the experimental and theoretical data is used to corroborate the synthesis of specific molecular structures. The (H(3)Ge)(x)SiH(4)(-)(x) family of compounds described here is not only of intrinsic molecular interest but also provides a unique route to a new class of Si-based semiconductors including epitaxial layers and coherent islands (quantum dots), with Ge-rich stoichiometries SiGe, SiGe(2), SiGe(3), and SiGe(4) reflecting the Si/Ge content of the corresponding precursor. The layers grow directly on Si(100) at unprecedented low temperatures of 300-450 degrees C and display homogeneous compositional and strain profiles, low threading defect densities, and atomically planar surfaces circumventing entirely the need for conventional graded compositions or lift-off technologies. The activation energies of all Si-Ge hydride reactions on Si(100) (E(a) approximately 1.5-2.0 eV) indicate high reactivity profiles with respect to H(2) desorption, consistent with the low growth temperatures of the films. The quantum dots are obtained exclusively at higher temperatures (T > 500 degrees C) and represent a new family of Ge-rich compositions with narrow size distribution, defect-free microstructures, and homogeneous, precisely tuned elemental content at the atomic level.

ChemInform, 2003

System. -Epitaxial SiCAlN films with single-phase wurtzite structures are grown on 6H-SiC by mole... more System. -Epitaxial SiCAlN films with single-phase wurtzite structures are grown on 6H-SiC by molecular beam epitaxy via reactions of H 3 SiCN and Al atoms at unprecedented low temperatures in the range of 550-750°C. The material has a fundamental bandgap of 3.2 eV consistent with theoretical calculations of the band structure. It is suggested that bandgap engineering between 3.2 and 4.5 eV is readily attainable by increasing the AlN content in the films. The microhardness of these films is comparable with that of sapphire. The SiCAlN films can be grown directly on Si substrates via self assembled Si-Al-O-N templates and buffer layers. The Si-Al-O-N materials are ideal candidates as semiconducting nucleation layers for the integration of nitride semiconductors such as AlN and GaN with silicon. -(TOLLE, J.; ROUCKA, R.; CHIZMESHYA, A. V. G.; CROZIER, P. A.; SMITH, D. J.; TSONG, I. S. T.; KOUVETAKIS*, J.; Solid State Sci. 4 (2002) 11-12, 1509-1519; Dep. Chem. Biochem., Ariz. State Univ., Tempe, AZ 85287, USA; Eng.) -W. Pewestorf 13-009

ChemInform, 2007

Germanium I 4700 ClnH6-nSiGe Compounds for CMOS Compatible Semiconductor Applications: Synthesis ... more Germanium I 4700 ClnH6-nSiGe Compounds for CMOS Compatible Semiconductor Applications: Synthesis and Fundamental Studies. -The new family of chlorinated Si-Ge hydrides based on the formula ClnH6-nSiGe is synthesized for semiconductor applications by reaction with BCl3. The built-in Cl functionalities are specifically designed to facilitate selective growth compatible with CMOS processing. The compounds are characterized by NMR, FTIR, mass spectroscopy, and DFT calculations. Depositions of (III) and (VI) on Si at 380-450°C produce near stoichiometric SiGe films exhibiting monocrystalline microstructures, smooth surface morphologies, reduced defect densities, and unusual strain properties. -(TICE, J. B.; CHIZMESHYA, A. V. G.; ROUCKA, R.; TOLLE, J.; CHERRY, B. R.; KOUVETAKIS*, J.; J. Am. Chem. Soc. 129 (2007) 25, 7950-7960; Dep. Chem. Biochem., Ariz. State Univ., Tempe, AZ 85287, USA; Eng.) -W. Pewestorf 41-018

Molecular Engineering, 1996

Physical Review B, 1994

ABSTRACT

Physical Review B, 1988

... 15 FEBRUARY 1988-II Second-harmonic generation at metal surfaces using an extended Thomas —Fe... more ... 15 FEBRUARY 1988-II Second-harmonic generation at metal surfaces using an extended Thomas —Fermi-von Weizsacker theory ... Thomas-Fermi energy is capable of capturing an essen-tial part of the wave-mechanical behavior. ...

ChemInform, 1998

Bonding Trends in (NSF) 3 at High-Pressures.

MRS Proceedings, 1997

ABSTRACT

MRS Proceedings, 2002

Page 1. New Ge-Sn materials with adjustable bandgaps and lattice constants Matthew R. Bauer, 1 Jo... more Page 1. New Ge-Sn materials with adjustable bandgaps and lattice constants Matthew R. Bauer, 1 John Tolle, 1 AVG Chizmeshya, 2 S. Zollner, 3 J. Menendez, 4 and J. Kouvetakis 1 1 Department of Chemistry and Biochemistry ...

ChemInform, 2007

ABSTRACT We introduce a new chemical approach to the incorporation of high concentrations of acti... more ABSTRACT We introduce a new chemical approach to the incorporation of high concentrations of active n-dopant atoms into group-IV semiconductors via low temperature, low cost, high efficiency routes involving carbon-free single-source inorganic hydrides. Controlled substitution of As into Ge-based semiconductors is made possible by the use of As(GeH3)3, which furnishes structurally and chemically compatible AsGe3 molecular cores. As(GeH3)3 is synthesized in high purity yields (75%) via a new single-step method based on reactions of GeH3Br and As[Si(CH3)3]3, circumventing the need for toxic and unstable starting materials as used in earlier approaches. We demonstrate the development of a viable route to the entire family of compounds M(GeH3)3 {M = P, As, Sb}, suitable for doping or superdoping applications of a wide range of functional materials. The structural, vibrational, and thermochemical properties of M(GeH3)3 are simulated for the first time via density functional theory calculations using both all-electron and effective core potentials. The vibrational calculations are in excellent agreement with the observed infrared spectra and the thermochemical stability is predicted to decrease with increasing molecular mass, in accord with experimental observations. The simulated structures show that the Ge−M−Ge angles decrease with increasing M size and further resolve inconsistencies with earlier gas electron diffraction measurements of P(GeH3)3. Bulk supercell calculations are then used to study the formation free energy of P, As, and Sb incorporation in bulk Ge, as well as the bond and lattice strains induced by the dopant atoms in the host diamond-structure lattice. As a first example of the usability of the M(GeH3)3 family, we demonstrate the successful doping of metastable Ge1-ySny alloys. This represents a crucial step toward the goal of developing photonic devices, such as photodetectors and photovoltaic cells, based on Ge1-ySny. Infrared ellipsometry experiments demonstrate high carrier concentrations and excellent resistivities in As(GeH3)3-doped Ge1-ySny. The latter are only moderately higher than those measured in pure Ge for the same dopant levels.

Atomic and Molecular Beams, 2001

Surface Science Letters, 1989

ABSTRACT

MRS Proceedings, 2006

ABSTRACT Our experiences in research on nanoscience and technology using various microscopies to ... more ABSTRACT Our experiences in research on nanoscience and technology using various microscopies to observe materials synthesis reactions and to measure local (∼ 0.1-100 nm scale) structure and composition variations in solids provide some very useful examples to introduce students to important concepts of the field. The fundamental concept to illustrate is the nanometer length scale, of course, but other concepts such as mass and energy flows at the nanometer level and their effects on materials properties are at least as important, but more difficult to bring to students in a challenging but understandable way. We are using dynamic in situ or animated microscopy experiments in several material systems to teach these concepts. These experimental research results provide a useful basis for student computer modeling experiments, to give them direct participation in nanoscale materials research at an appropriate level. We are also exploring student group participation in live (interactive) electron microscopy experience via remote access into a suitably equipped computer visualization classroom.

Chemistry of Materials, 2014

IEEE Photonics Journal, 2010

We report new approaches based on rational design and preparation of chemical vapor deposition pr... more We report new approaches based on rational design and preparation of chemical vapor deposition precursors involving novel main-group hydrides to fabricate new families of Si-based semiconductors and prototype devices that display compositional and structural inheritance, from the parent molecule to the solid end product. This methodology enables materials synthesis at extraordinarily low temperatures that are compatible with complementary metal-oxide-semiconductor (CMOS) processing/selective growth and provides the means for obtaining highly metastable strain states in prototype structures that cannot be obtained by conventional protocols. Some of the materials and devices under development, involving alloys in the Si-Ge-Sn system, open up exciting opportunities in photodetectors and photovoltaics because they grow directly on cheap Si substrates and cover an extended range of the near-infrared spectrum that is not accessible to current photovoltaic and optoelectronic group IV semiconductors. impurities into the final product, thereby degrading device performance. On the other hand, the weakly bonded H ligands are readily eliminated as highly stable, noncorrosive H 2 , leaving groups leading to the highest possible purity in the final product at extraordinarily low temperatures that are well below the typical desorption range of H atoms in conventional CVD of semiconductors . Accordingly, the latter may serve as surfactants in the epitaxy-driven crystal assembly of materials possessing fundamentally incompatible surface energies. Our work to date provides mounting evidence that this metastable regime is responsible for the layer-by-layer growth of perfectly uniform and atomically flat heterostructures suitable for the development of thick device quality films. Most importantly, this low-temperature nontraditional processing is perfectly compatible with the fabrication of thermally sensitive device structures in typical back-end complementary metaloxide-semiconductor (CMOS) processes.

ChemInform, 2005

The synthesis of the entire silyl-germyl sequence of molecules (H(3)Ge)(x)SiH(4)(-)(x) (x = 1-4) ... more The synthesis of the entire silyl-germyl sequence of molecules (H(3)Ge)(x)SiH(4)(-)(x) (x = 1-4) has been demonstrated. These include the previously unknown (H(3)Ge)(2)SiH(2), (H(3)Ge)(3)SiH, and (H(3)Ge)(4)Si species as well as the H(3)GeSiH(3) analogue which is obtained in practical high-purity yields as a viable alternative to disilane and digermane for semiconductor applications. The molecules are characterized by FTIR, multinuclear NMR, mass spectrometry, and Rutherford backscattering. The structural, thermochemical, and vibrational properties are studied using density functional theory. A detailed comparison of the experimental and theoretical data is used to corroborate the synthesis of specific molecular structures. The (H(3)Ge)(x)SiH(4)(-)(x) family of compounds described here is not only of intrinsic molecular interest but also provides a unique route to a new class of Si-based semiconductors including epitaxial layers and coherent islands (quantum dots), with Ge-rich stoichiometries SiGe, SiGe(2), SiGe(3), and SiGe(4) reflecting the Si/Ge content of the corresponding precursor. The layers grow directly on Si(100) at unprecedented low temperatures of 300-450 degrees C and display homogeneous compositional and strain profiles, low threading defect densities, and atomically planar surfaces circumventing entirely the need for conventional graded compositions or lift-off technologies. The activation energies of all Si-Ge hydride reactions on Si(100) (E(a) approximately 1.5-2.0 eV) indicate high reactivity profiles with respect to H(2) desorption, consistent with the low growth temperatures of the films. The quantum dots are obtained exclusively at higher temperatures (T > 500 degrees C) and represent a new family of Ge-rich compositions with narrow size distribution, defect-free microstructures, and homogeneous, precisely tuned elemental content at the atomic level.

ChemInform, 2003

System. -Epitaxial SiCAlN films with single-phase wurtzite structures are grown on 6H-SiC by mole... more System. -Epitaxial SiCAlN films with single-phase wurtzite structures are grown on 6H-SiC by molecular beam epitaxy via reactions of H 3 SiCN and Al atoms at unprecedented low temperatures in the range of 550-750°C. The material has a fundamental bandgap of 3.2 eV consistent with theoretical calculations of the band structure. It is suggested that bandgap engineering between 3.2 and 4.5 eV is readily attainable by increasing the AlN content in the films. The microhardness of these films is comparable with that of sapphire. The SiCAlN films can be grown directly on Si substrates via self assembled Si-Al-O-N templates and buffer layers. The Si-Al-O-N materials are ideal candidates as semiconducting nucleation layers for the integration of nitride semiconductors such as AlN and GaN with silicon. -(TOLLE, J.; ROUCKA, R.; CHIZMESHYA, A. V. G.; CROZIER, P. A.; SMITH, D. J.; TSONG, I. S. T.; KOUVETAKIS*, J.; Solid State Sci. 4 (2002) 11-12, 1509-1519; Dep. Chem. Biochem., Ariz. State Univ., Tempe, AZ 85287, USA; Eng.) -W. Pewestorf 13-009

ChemInform, 2007

Germanium I 4700 ClnH6-nSiGe Compounds for CMOS Compatible Semiconductor Applications: Synthesis ... more Germanium I 4700 ClnH6-nSiGe Compounds for CMOS Compatible Semiconductor Applications: Synthesis and Fundamental Studies. -The new family of chlorinated Si-Ge hydrides based on the formula ClnH6-nSiGe is synthesized for semiconductor applications by reaction with BCl3. The built-in Cl functionalities are specifically designed to facilitate selective growth compatible with CMOS processing. The compounds are characterized by NMR, FTIR, mass spectroscopy, and DFT calculations. Depositions of (III) and (VI) on Si at 380-450°C produce near stoichiometric SiGe films exhibiting monocrystalline microstructures, smooth surface morphologies, reduced defect densities, and unusual strain properties. -(TICE, J. B.; CHIZMESHYA, A. V. G.; ROUCKA, R.; TOLLE, J.; CHERRY, B. R.; KOUVETAKIS*, J.; J. Am. Chem. Soc. 129 (2007) 25, 7950-7960; Dep. Chem. Biochem., Ariz. State Univ., Tempe, AZ 85287, USA; Eng.) -W. Pewestorf 41-018