Studies of the electrical properties of Si single crystals with delta(Sb) layers of various sheet densities ND, of Sb atoms (5×1012-3×1014 cm-2) have furnished detailed information about the low-temperature features of the electron... more
Studies of the electrical properties of Si single crystals with delta(Sb) layers of various sheet densities ND, of Sb atoms (5×1012-3×1014 cm-2) have furnished detailed information about the low-temperature features of the electron transport in this system. The metal-type conductivity of delta layers at ND>=3×1013 cm-2 exhibits manifestations of the weak localization of electrons and electron-electron interaction in a two-dimensional
Research Interests: Physics, Materials Science, Electron, Physical sciences, Electron Transport, and 13 morePhysical, Electron Density, Temperature Dependence, CHEMICAL SCIENCES, Anderson localization, Single Crystal, Electrical Properties, QC, Low Temperature, Electric Field, Weak Localization, Current-Voltage Characteristic, and Relaxation Time
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Si/Si0.64Ge0.36/Si heterostructures have been grown at low temperature (450 °C) to avoid the strain-induced roughening observed for growth temperatures of 550 °C and above. The electrical properties of these structures are poor, and... more
Si/Si0.64Ge0.36/Si heterostructures have been grown at low temperature (450 °C) to avoid the strain-induced roughening observed for growth temperatures of 550 °C and above. The electrical properties of these structures are poor, and thought to be associated with grown-in point defects as indicated in positron annihilation spectroscopy. However, after an in situ annealing procedure (800 °C for 30 min) the
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Mobility and low-frequency (LF) noise were studied in tensile strained Si n- and pMOSFETs fabricated on relaxed SiGe virtual substrates. Both the impact of the channel orientation (〈110〉 or 〈100〉 on (100) Si) and the tensile strain were... more
Mobility and low-frequency (LF) noise were studied in tensile strained Si n- and pMOSFETs fabricated on relaxed SiGe virtual substrates. Both the impact of the channel orientation (〈110〉 or 〈100〉 on (100) Si) and the tensile strain were carefully investigated. Two types of virtual substrates were used; a thin relaxed SiGe layer (20% Ge) and a thick one (27% Ge).
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ABSTRACTIn this paper we address the problem of producing SiGe buffer layers of acceptable quality for the growth of symmetrically strained SiGe structures. Initially we consider SiGe layers grown to well beyond the metastable critical... more
ABSTRACTIn this paper we address the problem of producing SiGe buffer layers of acceptable quality for the growth of symmetrically strained SiGe structures. Initially we consider SiGe layers grown to well beyond the metastable critical thickness and examine the degree of residual strain both as - grown and post anneal. The defect levels in metastable SiGe layers following high temperature anneal were also studied. A buffer layer was grown consisting of stacked metastable SiGe layers each of which is annealed in situ prior to the growth of the next layer and terminating with a 0.45 SiGe alloy. This produces nearly fully relaxed 1.15pim thick structures with threading dislocation densities of 4 × 106cm−2. Limited area growth on Si suggests that elastically relaxed material free of both threading and misfit dislocations can be produced.
ABSTRACT The thermal conductivity and the thermoelectric power of two dimensional hole and electron gases in B and Sb delta-doped Si structures have been measured for the first time. The temperature range was 1.4 K to 30 K, and carrier... more
ABSTRACT The thermal conductivity and the thermoelectric power of two dimensional hole and electron gases in B and Sb delta-doped Si structures have been measured for the first time. The temperature range was 1.4 K to 30 K, and carrier sheet densities were in the range 0.3 to 1.0×1014 cm-2. Kohn anomalies have been observed in all samples. The thermopower is dominated by the phonon drag contribution in each case. Calculations of the temperature dependence of the thermopower agree with experimental data when unscreened phonon scattering potentials are used for Si:B and Si:Sb.
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The hole mobility has been measured in a metal-oxide semiconductor field-effect transistor featuring a 6 nm Si0.5Ge0.5 conduction channel. Physical characterization and analysis of the electrical properties confirm that the channel is... more
The hole mobility has been measured in a metal-oxide semiconductor field-effect transistor featuring a 6 nm Si0.5Ge0.5 conduction channel. Physical characterization and analysis of the electrical properties confirm that the channel is fully strained. At a total sheet carrier concentration, ps, of 1012 cm-2, the 300 K mobility of 220 cm2 V-1 s-1 is double that of a Si control
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Low-temperature conductance mechanism in low-density Si/SiGe heterostructures in high magnetic fields (ultra-quantum limit) is studied using AC and DC transport measurements. Evidence of the Wigner crystal in this regime is given.
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ABSTRACT A silicon-superconductor tunnel junction is capable of cooling electrons from a temperature of 300 mK to 150 mK and below when a current is passed through it and may also be used as the thermometer in a silicon “cold electron... more
ABSTRACT A silicon-superconductor tunnel junction is capable of cooling electrons from a temperature of 300 mK to 150 mK and below when a current is passed through it and may also be used as the thermometer in a silicon “cold electron bolometer”. Recent work on these novel devices is described here.
ABSTRACT The effect of reactive ion etching (RIE) of Silicon (Si), Germanium (Ge) and highly phosphorous doped Germanium (Ge:P) in an SF6-O-2 plasma has been studied. We find that the etch characteristics of etch rate and sidewall profile... more
ABSTRACT The effect of reactive ion etching (RIE) of Silicon (Si), Germanium (Ge) and highly phosphorous doped Germanium (Ge:P) in an SF6-O-2 plasma has been studied. We find that the etch characteristics of etch rate and sidewall profile are greatly affected by the O-2 content. Etching rates of Ge and Ge: P depend on the O-2 content with a significant reduction up to 20% of O-2. We also find that an anisotropic sidewall etching mechanism exists and is dependent on the percentage of O-2 (% O-2) in the plasma. Sidewall angles range from a minimum of 66 degrees to a maximum of 166 degrees, where a critical concentration for etching angle exists where the etching angle can alternate from below 90 degrees to above 90 degrees. In combination, both features allow for precision plasma etching of Si, Ge and P:Ge.
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We describe a high sensitivity THz detector based on the hot electron effect in a highly doped thin silicon semiconducting layer with tunnelling contacts to superconducting islands (S-Sm-S).
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... Rev. 104, 1536 (1956). J.N. Mundy, L. W. Barr, and F.A. Smith, Phil. Mag. 14, 785 (1966). PHYSICAL RE VIEW B VOLUME 2, NUMBER 6 15 SE PTEMBER 1970 Effect of Interactions on the Kondo Resistivity of Dilute Au Fe Alloys* P.J. Ford, t... more
... Rev. 104, 1536 (1956). J.N. Mundy, L. W. Barr, and F.A. Smith, Phil. Mag. 14, 785 (1966). PHYSICAL RE VIEW B VOLUME 2, NUMBER 6 15 SE PTEMBER 1970 Effect of Interactions on the Kondo Resistivity of Dilute Au Fe Alloys* P.J. Ford, t T.E. Whall, and J.W. Loram ...
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... II. EXPERIMENTAL DETAILS Most of the alloys used in the present investi-gations were prepared from spectroscopically pure Au (estimated Fe content 5 ppm), 99. 999% pure Cu and 99. 95% pure Fe, all provided by Johnson Matthey and Co. ...
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Cyclotron resonance (CR) has been used to measure the effective mass of holes in a series of p-type modulation doped Si1-xGex/Si heterostructures, in which x varies from 0.05 to 0.29, and the two-dimensional carrier density... more
Cyclotron resonance (CR) has been used to measure the effective mass of holes in a series of p-type modulation doped Si1-xGex/Si heterostructures, in which x varies from 0.05 to 0.29, and the two-dimensional carrier density ps=(0.95-5.8)×1011 cm-2. The measured masses for these samples are, to the best of our knowledge, the lowest yet reported, with a mass as low as
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ABSTRACT This chapter presents some recent advances in the field of thermal energy harvesting, starting with thermoelectric energy harvesting, with a focus on the prospects of materials nanostructuration. Research toward alternative... more
ABSTRACT This chapter presents some recent advances in the field of thermal energy harvesting, starting with thermoelectric energy harvesting, with a focus on the prospects of materials nanostructuration. Research toward alternative solutions will also be presented. Thermoelectric (TE) conversion is the most straightforward method to convert thermal energy into electrical energy, able to power such systems as autonomous sensor networks. Raman thermometry offers particular advantages for a fast and contactless determination of the thermal conductivity. The highly porous Si material is nanostructured and has the properties of confined systems, including a very low thermal conductivity. The chapter explores an alternative route for thermal energy harvesting (TEH) with composites using the mechanical coupling between a thermal shape memory alloy (SMA) and a piezoelectric material.
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... Phys. Lett. SO 1166 [SI Van Gorkum AA, Nagakawa K and Shiraki Y 1987 Japan. J. Appl. Phys. 26 1933 161 Mattey N L, Hopkinson M, Houghton R F, McPhail D S, Whall TE, Parker E H C, Booker G R and Whitehurst J 1990 Thin Solid Films 184... more
... Phys. Lett. SO 1166 [SI Van Gorkum AA, Nagakawa K and Shiraki Y 1987 Japan. J. Appl. Phys. 26 1933 161 Mattey N L, Hopkinson M, Houghton R F, McPhail D S, Whall TE, Parker E H C, Booker G R and Whitehurst J 1990 Thin Solid Films 184 15 ...
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... Comprehensive two-dimensional simulations of devices using drift–diffusion (DD), and bulkMonte Carlo calibrated hydrodynamic (HD) and energy transport (ET) models have revealed enhanced high-field hole transport in strained-channel... more
... Comprehensive two-dimensional simulations of devices using drift–diffusion (DD), and bulkMonte Carlo calibrated hydrodynamic (HD) and energy transport (ET) models have revealed enhanced high-field hole transport in strained-channel MOSFETs. ...
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... Mod. Phys. 54 Asche M , Friedland K J, Kleinert P, Kostial H, Herzog J and Bishop D J, Dynes RC and Tsui D C 1982 Phys. Rev. B 26 Phys. ... lwahuchi S and Nagaoka Y 1989 J. Phys. Soc. Japan 58 1325 Kearney M J and Butcher P N I988 J.... more
... Mod. Phys. 54 Asche M , Friedland K J, Kleinert P, Kostial H, Herzog J and Bishop D J, Dynes RC and Tsui D C 1982 Phys. Rev. B 26 Phys. ... lwahuchi S and Nagaoka Y 1989 J. Phys. Soc. Japan 58 1325 Kearney M J and Butcher P N I988 J. Phys. C: Solid State Phys. ...
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The authors' report the highest 4 K hole mobility (9300 cm2 V-1 s-1) observed so far in a Si/SiGe/Si heterostructure. It is tentatively concluded that this improvement over previous results is due... more
The authors' report the highest 4 K hole mobility (9300 cm2 V-1 s-1) observed so far in a Si/SiGe/Si heterostructure. It is tentatively concluded that this improvement over previous results is due to a reduction in interface charge and that the mobility is now limited by interface roughness scattering.
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In this paper, we present a (scanning) transmission electron microscopy analysis of novel Ge-on-Si MOSFETs which incorporate a high-k HfO 2 dielectric and TaN/TiN metal gate electrodes. A key feature of these devices is the incorporation... more
In this paper, we present a (scanning) transmission electron microscopy analysis of novel Ge-on-Si MOSFETs which incorporate a high-k HfO 2 dielectric and TaN/TiN metal gate electrodes. A key feature of these devices is the incorporation of a very thin (~ 1nm) Si ...
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The Mössbauer spectra of FexO4-xFx at 295 and 75 are reported. Anionic substitutions of about x = 0.05 are sufficient to suppress the Verwey transition. A random distribution of fluorine ions induces changes in the B-sublattice giving... more
The Mössbauer spectra of FexO4-xFx at 295 and 75 are reported. Anionic substitutions of about x = 0.05 are sufficient to suppress the Verwey transition. A random distribution of fluorine ions induces changes in the B-sublattice giving rise to three different Fe(B) hyperfine fields, two having stronger Fe2+ character than the field found in pure magnetite. S.R.C. CASE student.
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Abstract Quantum dots of 50~ 60 nm diameter fabricated from both Si/Si 1-x Ge x (x= 0.1~ 0.3) strained layer superlattices and a strain symmetried Si 9/Ge 6 superlattice were investigated by a combination of Raman scattering,... more
Abstract Quantum dots of 50~ 60 nm diameter fabricated from both Si/Si 1-x Ge x (x= 0.1~ 0.3) strained layer superlattices and a strain symmetried Si 9/Ge 6 superlattice were investigated by a combination of Raman scattering, photoluminescence, and ...
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The magnitude and temperature of the Verwey transition have been investigated for germanium- and fluorine-doped magnetite to assess the effectiveness of A sublattice and anion substitutions in displacing and suppressing the transition. It... more
The magnitude and temperature of the Verwey transition have been investigated for germanium- and fluorine-doped magnetite to assess the effectiveness of A sublattice and anion substitutions in displacing and suppressing the transition. It is found that the quantity G=d ln(σT)/d(1/T), where σ is the conductivity, is more sensitive to the existence of the transition than σ itself: the consequence is that the presence of the transition can be detected to higher degrees of substitution than heretofore. The rate of variation of the Verwey temperature Tv with level of substitution and the condition for suppression of the transition are discussed.
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Research Interests: Engineering, Secondary Ion Mass Spectrometry, Applied Physics, Transmission Electron Microscopy, Atomic Force Microscopy, and 11 moreMolecular beam epitaxy, Transport Properties, Mathematical Sciences, Physical sciences, Low Energy Buildngs, Dislocations, Structure Analysis, Room Temperature, Cross Section, Active Layer, and Point Defect
... Because of the need to have a furnace around the alu-mina tube, the coils С are 6 cm apart and 4.2 cm from the sample: the reduction in signal due to this separation is com-pensated by having 27 000 turns (of 48SWG copper wire) on... more
... Because of the need to have a furnace around the alu-mina tube, the coils С are 6 cm apart and 4.2 cm from the sample: the reduction in signal due to this separation is com-pensated by having 27 000 turns (of 48SWG copper wire) on each of the coils, which ... Mallinson, J. Appi ...
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Silicon germanium pMOSFETs have been fabricated on novel silicon germanium virtual substrates. The SiGe virtual substrates were grown by MBE on 10µmx10µm silicon pillars fabricated by dry etching trenches into the original silicon... more
Silicon germanium pMOSFETs have been fabricated on novel silicon germanium virtual substrates. The SiGe virtual substrates were grown by MBE on 10µmx10µm silicon pillars fabricated by dry etching trenches into the original silicon substrate. The pillars promote relaxation of the SiGe virtual substrate and reduce cross hatch on the wafer surface. The devices have 5nm silicon germanium active layer with
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Temperature (1.6–20K) and magnetic field (up to 2.5T) dependences of quantum corrections to the conductivity and Hall coefficient ofSi epitaxial films containing a δSb>-layer of different sheet densityN Sb are studied. The quantum... more
Temperature (1.6–20K) and magnetic field (up to 2.5T) dependences of quantum corrections to the conductivity and Hall coefficient ofSi epitaxial films containing a δSb>-layer of different sheet densityN Sb are studied. The quantum corrections are due to the effects of electron weak localization (WL) and electron-electron interaction (EEI). Analysis of the quantum corrections made it possible to determine the temperature dependence of electron phase relaxation time τϕ, the spin-orbit interaction time τ80 and the screening factorF. It is found that the dependence τϕ(T) is determined by the electron-electron scattering processes, τϕ∝T −p withp≈1, and an increase in the parameterF with decreasing electron concentrationn in the δ-layer is related to the specific features of the screening processes in two-dimensional electron systems.
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For the first time, we have demonstrated the reduced low-frequency (LF) noise in sub-μm metamorphic high Ge content p-Si0.3Ge0.7 MOSFETs in comparison with p-Si MOSFETs at 293K. Three times lower LF noise over 1–100Hz range at VDS=−50mV... more
For the first time, we have demonstrated the reduced low-frequency (LF) noise in sub-μm metamorphic high Ge content p-Si0.3Ge0.7 MOSFETs in comparison with p-Si MOSFETs at 293K. Three times lower LF noise over 1–100Hz range at VDS=−50mV and VG−VTH=−1.5V was measured for the 0.55μm effective gate length p-Si0.3Ge0.7 MOSFET compared with p-Si MOSFET. Over three times drain current enhancement in
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... SM Sze: Physics of Semiconductor Devices (Wiley, New York 1969) 14. EH Putley: The Hall Effect and Related Phenomena (Butter-worth, London 1960) 15. FJ Morin, JP Malta: Phys. Rev. 96, 28 (1954) 16. R.Houghton, R.AA.Kubiak, WYLeong,... more
... SM Sze: Physics of Semiconductor Devices (Wiley, New York 1969) 14. EH Putley: The Hall Effect and Related Phenomena (Butter-worth, London 1960) 15. FJ Morin, JP Malta: Phys. Rev. 96, 28 (1954) 16. R.Houghton, R.AA.Kubiak, WYLeong, EHC Parker: In preparation 17. ...
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A method to calculate a smooth electrical conductivity versus mobility plot ("mobility spectrum") from the classical magnetoconductivity tensor in heterogeneous structures with the help of a "maximum entropy principle"... more
A method to calculate a smooth electrical conductivity versus mobility plot ("mobility spectrum") from the classical magnetoconductivity tensor in heterogeneous structures with the help of a "maximum entropy principle" has been developed. In this approach the closeness of the fit and the entropy of the mobility spectrum are optimized. The spectrum is then the most probable one with the least influence of the personal bias of the investigator for any given set of experimental data and is maximally noncommittal with regard to the unmeasured data. The advantages of the maximum entropy mobility spectrum analysis as compared to the conventional mobility spectrum analysis are demonstrated using a synthetic dataset.
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In this paper, we present a transmission electron microscopy analysis of novel Ge-on-Si MOSFETs using a JEOL 2010F and an aberration-corrected JEOL 2200FSC. A key feature of these devices is the incorporation of a very thin (~1nm) Si... more
In this paper, we present a transmission electron microscopy analysis of novel Ge-on-Si MOSFETs using a JEOL 2010F and an aberration-corrected JEOL 2200FSC. A key feature of these devices is the incorporation of a very thin (~1nm) Si passivation layer on top of the Ge virtual substrate, which is partially oxidised to form SiO2 (~0.5nm) prior to depositing HfO2 dielectric. We will show that the thin SiO2 layer is not purely amorphous but has some degree of crystal ordering due to being bonded to crystalline materials. Moreover, we will examine the presence of small monolayer variation in Si/SiO2 interface roughness.