S. Campbell | University of Minnesota (original) (raw)

Papers by S. Campbell

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 1993

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2004

A system has been designed to generate monodisperse, single crystal silicon nanoparticles. The pa... more A system has been designed to generate monodisperse, single crystal silicon nanoparticles. The particles are generated using a SiH 4 /H 2 mixture in a high density plasma. An aerodynamic lens assembly focuses and size selects the particles. A high voltage plate is used to accelerate the charged particles such that they can be injected into a high temperature annealing tube to be heated. The shape and structure of the particles are changed in the annealing tube. Single crystals are obtained.

2009 Device Research Conference, 2009

In summary, this paper demonstrates fixed-beam switches using well-aligned composite SWNT membran... more In summary, this paper demonstrates fixed-beam switches using well-aligned composite SWNT membranes can be switched at low voltage and high frequency. The measured DC pull-in voltages ranged from 0.9V to 4.8 V depending on the length of the switch. AC measurements indicate a switching delay as low as 600 psec for 300 nm beams. This new SWNT composite membrane switch

2010 35th IEEE Photovoltaic Specialists Conference, 2010

This paper uses numerical simulation to study the effects of Ga concentration profile on the perf... more This paper uses numerical simulation to study the effects of Ga concentration profile on the performance of CuIn1-xGaxSe2 (CIGS) solar cell, including the effects of acceptor type Cu antisite defects whose concentration depends on Ga composition. These defects are the dominant deep traps in the CIGS material system. The concentration and spatial distribution of these traps affect the solar cell

Journal of Applied Physics, 2003

ABSTRACT

Journal of Applied Physics, 2008

ABSTRACT To explore the possibility of bandgap engineering in binary systems of oxide insulators ... more ABSTRACT To explore the possibility of bandgap engineering in binary systems of oxide insulators we studied photoconductivity of nanometer-thin Hf oxide layers containing different concentrations of cations of different sorts (Si, Al, Sr, or Ce) deposited on (100)Si. The lowest bandgap of the Hf:Al oxide is close to the value 6–6.2 eV of elemental amorphous Al 2 O 3 and insensitive to the Al content for concentrations of Al exceeding 36%. This result suggests that the Al oxide subnetwork with the largest bandgap preserves this energy width while development of a narrower gap of HfO 2 is prevented possibly by dilution of the second cation subnetwork. When Ce is admixed to HfO 2 an intermediate bandgap value (between the CeO 2 and HfO 2 bandgap widths) of 5.3+0.1 eV is observed for all concentrations of Ce, suggesting that the electronic structure of both elemental oxide subnetworks which form the binary metal oxide system, is affected. In Hf:Si oxide samples photoconductivity thresholds of 5.6–5.9 eV corresponding to the bandgap of HfO 2 are observed for all studied Si concentrations, suggesting phase separation to occur. The photoconductivity of SrHfO 3 exhibits two thresholds at 4.4 and 5.7 eV, which are close to the bandgaps of elemental SrO and HfO 2 , respectively, indicating, again, phase separation. Through this work we have illustrated photoconductivity as a feasible method to trace phase separation in nanometer-thin layers of binary systems of metal oxides.

Applied Physics Letters, 2006

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Journal of Applied Physics, 2004

ABSTRACT

MRS Proceedings

The electrical reliability properties of PZT (54/46) thin films have been measured for the purpos... more The electrical reliability properties of PZT (54/46) thin films have been measured for the purpose of integrating this material with silicon-based microelectromechanical systems. Ferroelectric thin films of PZT were prepared by metal organic decomposition. The charge trapping and degradation properties of these thin films were studied through device characteristics such as hysteresis loop, leakage current, fatigue, dielectric constant, capacitancevoltage, and loss factor measurements. Several unique experimental results have been found. Different degradation processes were verified through fatigue (bipolar stress), low and high charge injection (unipolar stress), and high field stressing (unipolar stress).

Nanotechnology, Jan 12, 2018

Zinc oxide (ZnO) nanocrystal films are of interest for new applications in thin film transistors ... more Zinc oxide (ZnO) nanocrystal films are of interest for new applications in thin film transistors and as transparent conductive oxides. Previous work has concentrated on achieving highly conductive, metallic films. This work focusses on the less explored insulating to semi-insulating regime, which enables obtaining deeper insights into the roles of surface states and defect states trapped at the nanocrystal interfaces. We examine the effects of various post-deposition treatments including controlled dosing with ultraviolet light, filling the voids between nanocrystals with a matrix material deposited by atomic layer deposition, and thermal annealing of the nanocrystal films. Both Mott and Efros-Shklovskii variable range hopping are observed depending on the carrier concentration in the nanocrystals. Using the above post-treatments to transition the films between the two conduction mechanisms enables determining the Fermi level density of states and the electron localization length. T...

IEEE MTT-S International Microwave Symposium Digest

ABSTRACT

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures

ABSTRACT

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures

ABSTRACT

Physical Review Letters

where R* is the binding energy of excitons,~is the dielectric constant, and~* is the reduced mass... more where R* is the binding energy of excitons,~is the dielectric constant, and~* is the reduced mass of excitons. If we take~*=0.03@&, estimated from the cyclotron mass of electrons and holes at 88 T and & =100, we obtain y =2890 at 88 T. The binding energy of excitons is then estimated to be 4.6 meV. " Thus it is worthwhile to investigate in more detail this interesting problem of the phase transition which might occur near the gapless state in very high magnetic fields.

MRS Proceedings

To develop a high-κ gate dielectric for replacing SiO2 in MOSFETs, multi-component metal oxides c... more To develop a high-κ gate dielectric for replacing SiO2 in MOSFETs, multi-component metal oxides could have advantages over single metal oxides because they may offer higher dielectric constants (κ's) as well as other favorable properties. To find the film composition for obtaining a good dielectric from the given component oxides is a time-consuming and costly process for multi-component systems. Recently, we reported a combinatorial chemical vapor deposition (CVD) technique to deposit compositional spreads of ternary metal-oxides for high-κ dielectrics. In this work, compositional spreads of ZrO2, TiO2, SnO2 and HfO2 were deposited using anhydrous metal nitrates. By measuring chemical composition, film thickness, and electrical properties, we are able to map κ and establish its dependence on film composition. This high-throughput deposition technique allows us to generate a compositional library quickly for screening material properties. In addition, a crystalline phase which d...

ChemInform

ABSTRACT In this paper we present the development of a technique for anisotropically etching sili... more ABSTRACT In this paper we present the development of a technique for anisotropically etching silicon on GeSi. Wet chemical etching exhibits a selectivity of nearly 40:1 but is completely isotropic and requires the use of a hard mask. The fluorine plasma process which has been reported in the literature as having high selectivity was nonreproducible as a result of significant polymeric deposition on the chamber surfaces. Furthermore the etch residue was not easily removed in an O 2 plasma and led to highly resistive contacts. Reactive ion etch processes using BCl 3 /Cl 2 and SiCl 4 were found to anisotropically etch the silicon layer, but had poor selectively to GeSi. By combining a reactive ion etch at 300 W forward power and 20 mTurr in SiCl 4 , with a wet chemical dip, an adequate process for selectively patterning submicron features was obtained.

Materials Science in Semiconductor Processing

We report on a low-temperature electron spin resonance (ESR) study of (100)Si/HfO2 entities with ... more We report on a low-temperature electron spin resonance (ESR) study of (100)Si/HfO2 entities with ultrathin layers of amorphous (a)- HfO2 deposited by distinct chemical vapor deposition (CVD) techniques using chemically different precursors. The incorporation of N is revealed in (100)Si/HfO2 structures with ultrathin a-HfO2 films deposited by CVD using Hf(NO3)4 as precursor: Upon 60Co γ-irradiation, a prominent ESR powder pattern is observed, which via ESR measurements at two observational frequencies has been incontrovertibly identified as originating from NO2 radicals (density ⩾55atppm). The molecules are found to be stabilized and likely homogeneously distributed in the a-HfO2 network. Based on symmetry considerations, it is suggested that during deposition, N is incorporated in the HfO2 network as neutral N≡O3 precursors, which are transformed into ESR-active NO2 radicals upon γ-irradiation. The N incorporation appears inherent to the particular nitrado CVD process, an aspect that may bear on the electrical properties of the insulator, such as, e.g., introducing charge traps.

Springer Proceedings in Physics

The miniaturization of semiconductor devices brings the impending need for nanoscale components f... more The miniaturization of semiconductor devices brings the impending need for nanoscale components for which nanoparticles of semiconductor materials are uniquely suited. However, their small length scales are known to produce properties unique from those of their bulk form. Full characterization of the nanoparticles suggested for use in devices becomes imperative. This study investigates silicon nanocubes prepared by a constricted-mode capacitive

Journal of Vacuum Science & Technology A, 1996

ABSTRACT

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 1993

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2004

A system has been designed to generate monodisperse, single crystal silicon nanoparticles. The pa... more A system has been designed to generate monodisperse, single crystal silicon nanoparticles. The particles are generated using a SiH 4 /H 2 mixture in a high density plasma. An aerodynamic lens assembly focuses and size selects the particles. A high voltage plate is used to accelerate the charged particles such that they can be injected into a high temperature annealing tube to be heated. The shape and structure of the particles are changed in the annealing tube. Single crystals are obtained.

2009 Device Research Conference, 2009

In summary, this paper demonstrates fixed-beam switches using well-aligned composite SWNT membran... more In summary, this paper demonstrates fixed-beam switches using well-aligned composite SWNT membranes can be switched at low voltage and high frequency. The measured DC pull-in voltages ranged from 0.9V to 4.8 V depending on the length of the switch. AC measurements indicate a switching delay as low as 600 psec for 300 nm beams. This new SWNT composite membrane switch

2010 35th IEEE Photovoltaic Specialists Conference, 2010

This paper uses numerical simulation to study the effects of Ga concentration profile on the perf... more This paper uses numerical simulation to study the effects of Ga concentration profile on the performance of CuIn1-xGaxSe2 (CIGS) solar cell, including the effects of acceptor type Cu antisite defects whose concentration depends on Ga composition. These defects are the dominant deep traps in the CIGS material system. The concentration and spatial distribution of these traps affect the solar cell

Journal of Applied Physics, 2003

ABSTRACT

Journal of Applied Physics, 2008

ABSTRACT To explore the possibility of bandgap engineering in binary systems of oxide insulators ... more ABSTRACT To explore the possibility of bandgap engineering in binary systems of oxide insulators we studied photoconductivity of nanometer-thin Hf oxide layers containing different concentrations of cations of different sorts (Si, Al, Sr, or Ce) deposited on (100)Si. The lowest bandgap of the Hf:Al oxide is close to the value 6–6.2 eV of elemental amorphous Al 2 O 3 and insensitive to the Al content for concentrations of Al exceeding 36%. This result suggests that the Al oxide subnetwork with the largest bandgap preserves this energy width while development of a narrower gap of HfO 2 is prevented possibly by dilution of the second cation subnetwork. When Ce is admixed to HfO 2 an intermediate bandgap value (between the CeO 2 and HfO 2 bandgap widths) of 5.3+0.1 eV is observed for all concentrations of Ce, suggesting that the electronic structure of both elemental oxide subnetworks which form the binary metal oxide system, is affected. In Hf:Si oxide samples photoconductivity thresholds of 5.6–5.9 eV corresponding to the bandgap of HfO 2 are observed for all studied Si concentrations, suggesting phase separation to occur. The photoconductivity of SrHfO 3 exhibits two thresholds at 4.4 and 5.7 eV, which are close to the bandgaps of elemental SrO and HfO 2 , respectively, indicating, again, phase separation. Through this work we have illustrated photoconductivity as a feasible method to trace phase separation in nanometer-thin layers of binary systems of metal oxides.

Applied Physics Letters, 2006

ABSTRACT

Journal of Applied Physics, 2004

ABSTRACT

MRS Proceedings

The electrical reliability properties of PZT (54/46) thin films have been measured for the purpos... more The electrical reliability properties of PZT (54/46) thin films have been measured for the purpose of integrating this material with silicon-based microelectromechanical systems. Ferroelectric thin films of PZT were prepared by metal organic decomposition. The charge trapping and degradation properties of these thin films were studied through device characteristics such as hysteresis loop, leakage current, fatigue, dielectric constant, capacitancevoltage, and loss factor measurements. Several unique experimental results have been found. Different degradation processes were verified through fatigue (bipolar stress), low and high charge injection (unipolar stress), and high field stressing (unipolar stress).

Nanotechnology, Jan 12, 2018

Zinc oxide (ZnO) nanocrystal films are of interest for new applications in thin film transistors ... more Zinc oxide (ZnO) nanocrystal films are of interest for new applications in thin film transistors and as transparent conductive oxides. Previous work has concentrated on achieving highly conductive, metallic films. This work focusses on the less explored insulating to semi-insulating regime, which enables obtaining deeper insights into the roles of surface states and defect states trapped at the nanocrystal interfaces. We examine the effects of various post-deposition treatments including controlled dosing with ultraviolet light, filling the voids between nanocrystals with a matrix material deposited by atomic layer deposition, and thermal annealing of the nanocrystal films. Both Mott and Efros-Shklovskii variable range hopping are observed depending on the carrier concentration in the nanocrystals. Using the above post-treatments to transition the films between the two conduction mechanisms enables determining the Fermi level density of states and the electron localization length. T...

IEEE MTT-S International Microwave Symposium Digest

ABSTRACT

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures

ABSTRACT

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures

ABSTRACT

Physical Review Letters

where R* is the binding energy of excitons,~is the dielectric constant, and~* is the reduced mass... more where R* is the binding energy of excitons,~is the dielectric constant, and~* is the reduced mass of excitons. If we take~*=0.03@&, estimated from the cyclotron mass of electrons and holes at 88 T and & =100, we obtain y =2890 at 88 T. The binding energy of excitons is then estimated to be 4.6 meV. " Thus it is worthwhile to investigate in more detail this interesting problem of the phase transition which might occur near the gapless state in very high magnetic fields.

MRS Proceedings

To develop a high-κ gate dielectric for replacing SiO2 in MOSFETs, multi-component metal oxides c... more To develop a high-κ gate dielectric for replacing SiO2 in MOSFETs, multi-component metal oxides could have advantages over single metal oxides because they may offer higher dielectric constants (κ's) as well as other favorable properties. To find the film composition for obtaining a good dielectric from the given component oxides is a time-consuming and costly process for multi-component systems. Recently, we reported a combinatorial chemical vapor deposition (CVD) technique to deposit compositional spreads of ternary metal-oxides for high-κ dielectrics. In this work, compositional spreads of ZrO2, TiO2, SnO2 and HfO2 were deposited using anhydrous metal nitrates. By measuring chemical composition, film thickness, and electrical properties, we are able to map κ and establish its dependence on film composition. This high-throughput deposition technique allows us to generate a compositional library quickly for screening material properties. In addition, a crystalline phase which d...

ChemInform

ABSTRACT In this paper we present the development of a technique for anisotropically etching sili... more ABSTRACT In this paper we present the development of a technique for anisotropically etching silicon on GeSi. Wet chemical etching exhibits a selectivity of nearly 40:1 but is completely isotropic and requires the use of a hard mask. The fluorine plasma process which has been reported in the literature as having high selectivity was nonreproducible as a result of significant polymeric deposition on the chamber surfaces. Furthermore the etch residue was not easily removed in an O 2 plasma and led to highly resistive contacts. Reactive ion etch processes using BCl 3 /Cl 2 and SiCl 4 were found to anisotropically etch the silicon layer, but had poor selectively to GeSi. By combining a reactive ion etch at 300 W forward power and 20 mTurr in SiCl 4 , with a wet chemical dip, an adequate process for selectively patterning submicron features was obtained.

Materials Science in Semiconductor Processing

We report on a low-temperature electron spin resonance (ESR) study of (100)Si/HfO2 entities with ... more We report on a low-temperature electron spin resonance (ESR) study of (100)Si/HfO2 entities with ultrathin layers of amorphous (a)- HfO2 deposited by distinct chemical vapor deposition (CVD) techniques using chemically different precursors. The incorporation of N is revealed in (100)Si/HfO2 structures with ultrathin a-HfO2 films deposited by CVD using Hf(NO3)4 as precursor: Upon 60Co γ-irradiation, a prominent ESR powder pattern is observed, which via ESR measurements at two observational frequencies has been incontrovertibly identified as originating from NO2 radicals (density ⩾55atppm). The molecules are found to be stabilized and likely homogeneously distributed in the a-HfO2 network. Based on symmetry considerations, it is suggested that during deposition, N is incorporated in the HfO2 network as neutral N≡O3 precursors, which are transformed into ESR-active NO2 radicals upon γ-irradiation. The N incorporation appears inherent to the particular nitrado CVD process, an aspect that may bear on the electrical properties of the insulator, such as, e.g., introducing charge traps.

Springer Proceedings in Physics

The miniaturization of semiconductor devices brings the impending need for nanoscale components f... more The miniaturization of semiconductor devices brings the impending need for nanoscale components for which nanoparticles of semiconductor materials are uniquely suited. However, their small length scales are known to produce properties unique from those of their bulk form. Full characterization of the nanoparticles suggested for use in devices becomes imperative. This study investigates silicon nanocubes prepared by a constricted-mode capacitive

Journal of Vacuum Science & Technology A, 1996

ABSTRACT