Amjad Nazzal - Academia.edu (original) (raw)

Papers by Amjad Nazzal

Applied Physics Letters, 2014

Temperature-dependent photoluminescence (PL) study has been conducted in Ge1−xSnx films with Sn c... more Temperature-dependent photoluminescence (PL) study has been conducted in Ge1−xSnx films with Sn compositions of 0.9%, 3.2%, and 6.0% grown on Si. The competing between the direct and indirect bandgap transitions was clearly observed. The relative peak intensity of direct transition with respect to the indirect transition increases with an increase in temperature, indicating the direct transition dominates the PL at high temperature. Furthermore, as Sn composition increases, a progressive enhancement of direct transition was observed due to the reduction of direct-indirect valley separation, which experimentally confirms that the Ge1−xSnx could become the group IV-based direct bandgap material grown on Si by increasing the Sn content.

CLEO: 2015, 2015

Temperature-dependent electroluminescence from a double heterostructure n-Ge/i-Ge<sub>0.94&... more Temperature-dependent electroluminescence from a double heterostructure n-Ge/i-Ge_0.94Sn_0.06/p-Ge LED was studied. The peak position of EL spectra showed a blue-shift as the temperature decreased. A maximum emission power of 7 mW was obtained under the current density of 800 A/cm².

11th International Conference on Group IV Photonics (GFP), 2014

The Ge/Ge0.94Sn0.06/Ge double heterostructure was grown on a Si substrate via chemical vapor depo... more The Ge/Ge0.94Sn0.06/Ge double heterostructure was grown on a Si substrate via chemical vapor deposition (CVD). The temperature and pump power-dependent photoluminescence (PL) were investigated and the enhanced direct transition at intense pump power was observed.

Applied Physics Letters, 2014

Material and optical characterizations have been conducted for epitaxially grown Ge1−xSnx thin fi... more Material and optical characterizations have been conducted for epitaxially grown Ge1−xSnx thin films on Si with Sn composition up to 10%. A direct bandgap Ge0.9Sn0.1 alloy has been identified by temperature-dependent photoluminescence (PL) study based on the single peak spectrum and the narrow line-width. Room temperature PL emission as long as 2230 nm has also been observed from the same sample.

2014 IEEE Photonics Conference, 2014

The interdigitated electrodes were integrated on Ge0.93Sn0.07/Ge heterostructure photoconductive ... more The interdigitated electrodes were integrated on Ge0.93Sn0.07/Ge heterostructure photoconductive detectors. Photoresponse extending to 2.2 μm was achieved, and the enhanced responsivity with reduced spacing between interdigitated electrodes was observed at room temperature.

Journal of Electronic Materials, 2014

High-quality compressive-strained Ge 1Àx Sn x /Ge films have been deposited on Si(001) substrate ... more High-quality compressive-strained Ge 1Àx Sn x /Ge films have been deposited on Si(001) substrate using a mainstream commercial chemical vapor deposition reactor. The growth temperature was kept below 450°C to be compatible with Si complementary metal-oxide-semiconductor processes. Germanium tin (Ge 1Àx Sn x) layers were grown with different Sn composition ranging from 0.9% to 7%. Material characterizations, such as secondary-ion mass spectrometry, Rutherford backscattering spectrometry, and x-ray diffraction analysis, show stable Sn incorporation in the Ge lattice. Comparison of the Sn mole fractions obtained using these methods shows that the bowing factor of 0.166 nm (in Vegard's law) is in close agreement with other experimental data. High-resolution transmission electron microscopy and atomic force microscopy results show that the films have started to relax through the formation of misfit and threading dislocations. Raman spectroscopy, ellipsometry, and photoluminescence (PL) techniques are used to study the structural and optical properties of the films. Room-temperature PL of the films shows that 7% Sn incorporation in the Ge lattice results in a decrease in the direct bandgap of Ge from 0.8 eV to 0.56 eV.

CLEO: 2014, 2014

ABSTRACT Photoluminescence (PL) from Ge1-xSnx grown on Si by CVD was investigated for Sn composit... more ABSTRACT Photoluminescence (PL) from Ge1-xSnx grown on Si by CVD was investigated for Sn composition of 0.9, 3.2, 6, and 7%, respectively. The direct and indirect band transitions were analyzed at different temperatures.

Bulletin of the American Physical Society, 2016

Submitted for the MAR16 Meeting of The American Physical Society Hybrid DFT calculations of the b... more Submitted for the MAR16 Meeting of The American Physical Society Hybrid DFT calculations of the band structure of alpha-Sn ERIN DUPAY1, LUCAS DOMULEVICZ2, HENRY CASTEJON3, AMJAD NAZZAL4, Wilkes Univ — The electronic properties of bulk alpha-tin were revisited using first principles. The band structure, in addition to other properties, such as the absorption spectrum and density of states, were calculated using Density Functional Theory and the HSE06 hybrid functional. The direct and indirect band gaps obtained from these calculations are in better agreement with experimental results than previously reported calculations. 1Graduate Student 2Undergraduate Student 3Faculty 4faculty Amjad Nazzal Wilkes Univ Date submitted: 06 Nov 2015 Electronic form version 1.4

Technical Digest. Summaries of papers presented at the Quantum Electronics and Laser Science Conference. Postconference Technical Digest (IEEE Cat. No.01CH37172)

Summary form only given. Recently, it has been demonstrated that the shape of CdSe nanocrystals c... more Summary form only given. Recently, it has been demonstrated that the shape of CdSe nanocrystals can be manipulated by controlling the growth kinetics (Peng et al, Nature, vol. 404, p. 59, 2000). The resulting nanostructures can be from a nearly spherical morphology to a rod-like one. The quantum confined nano-rods (quantum rods) can grow up to 200 nm long with an aspect ratio of up to 50. The successful growth of these rod- and wire-like structures provides a testing ground for studying the shape-dependent electronic and optical properties of nanocrystals and the quantum confinement effects in one-dimensional (1D) and quasi-1D regime, and in comparison with much characterized zero-dimensional (OD) quantum-dot system. Consequently, studies of quantum-rod system will explore another dimension for device applications of colloidal nanocrystals. In this paper, we report the optical studies of single CdSe quantum rods using far-field microscopic techniques.

ABSTRACT Ge 1−xSnx thin films with Sn composition up to 7% were epitaxially grown by chemical vap... more ABSTRACT Ge 1−xSnx thin films with Sn composition up to 7% were epitaxially grown by chemical vapor deposition on silicon. Temperature-dependent photoluminescence was investigated and the peaks corresponding to the direct and indirect transitions were observed in a wavelength range from 1.6 to 2.2 μm. The exact peak positions obtained from Gaussian fitting were fitted with an empirical temperature dependent band-gap equation (Varshni relationship). The separation between direct and indirect peaks was equal to 0.012 eV for GeSn thin film with 7% Sn content at room temperature. This observation indicates that the indirect-to-direct crossover would take place at slightly higher Sn compositions.

Applied Physics Letters, 2014

The Journal of Physical Chemistry B, 2004

We report our systematic studies of the environmental effects on the photoluminescence (PL) from ... more We report our systematic studies of the environmental effects on the photoluminescence (PL) from colloidal CdSe nanocrystals (NCs) embedded in polymer thin films. The highly luminescent bare-core CdSe NCs were significantly more robust than the core/shell CdSe/ZnS NCs against photoannealing under inert environments, while the core/shell NCs are more resistant to photooxidation. For the case of bare-core NCs, we show the importance of the initial photoactivation as the proper treatment for subsequent studies, a step that is basically irrelevant in the case of core/shell NCs. By measuring the PL wavelength shift, PL line width, and PL intensity, we investigated the dynamic changes of the emission properties of these NCs under different environments, including argon, oxygen, air, water vapor, and wet oxygen, and under different excitation conductions to reveal the photoinduced nature of the interactions between the nanocrystal surface and the environment. Mechanisms related to photoactivation, photooxidation, and PL enhancement are briefly discussed.

CLEO: 2014, 2014

GeSn/Ge heterostructure microdisks integrated on Si were fabricated. The quality of material grow... more GeSn/Ge heterostructure microdisks integrated on Si were fabricated. The quality of material grown by CVD was investigated and the photoluminescence spectrum was measured using a Ti:Sapphire laser as an excitation source under variable pump powers.

Physical Review B, 1995

... (7) (the so-called potential lineup)is extracted fromsimi-lar calculations for supercells con... more ... (7) (the so-called potential lineup)is extracted fromsimi-lar calculations for supercells containing thick slabs of the two materials. The macroscopic averaging used to calculate V„, was performed using the moving-slab averaging technique of Baldereschi, Baroni, and Resta. ...

Physical Review B, 2001

Excitation and emission spectra of CdSe single quantum rods with aspect ratios of 2 and 4 were in... more Excitation and emission spectra of CdSe single quantum rods with aspect ratios of 2 and 4 were investigated by far-field microscopic technique. Typical spectral linewidths of the rods are less than 60 meV at room temperature. Both excitation and emission of the single rods exhibit ...

Physical Review B, 2005

Organic-inorganic hybrid semiconductor ZnSe(C2H8N2)1/2 under hydrostatic pressure is studied usin... more Organic-inorganic hybrid semiconductor ZnSe(C2H8N2)1/2 under hydrostatic pressure is studied using a first-principles pseudopotential method with mixed-basis set, aimed at understanding its structural, mechanical, and electronic properties. The bulk modulus of the hybrid is determined to be 35.3GPa , which is considerably smaller than that of bulk ZnSe and, in fact, smaller than most known tetrahedral bulk semiconductors. We find that, when the hybrid is exposed to pressure, the chemical bonds of the inorganic constituent, not those of the organic constituent, are significantly compressed. This is important and allows the band-edge electronic properties of hybrid chalcogenides to be effectively tuned by applying pressure, since these properties can be substantially modified only by changing the inorganic Zn-Se bonds. Our calculations further demonstrate that the pressure dependence of the band gap in hybrid semiconductor shows an unusual nonlinearity, with a bowing coefficient that is more than one order of magnitude larger than in bulk ZnSe. Moreover, our results reveal that the in-plane electron mobility mass is notably small (me*˜0.27) and remains unchanged over a wide range of pressure. The hybrids will thus continue to maintain a fast electron mobility when they are under mechanical loading. However, and interestingly, the in-plane hole mass along the x and y direction is predicted to undergo at 2.14GPa a dramatic change from 0.35 to 2.2 and from 2.0 to 0.24, respectively. A pressure-induced isostructural phase transition is found to be responsible for this behavior of hole mass.

Nano Letters, 2003

Bulk and thin-film semiconductors are plausible materials for gas-sensing technologies. 1 In gene... more Bulk and thin-film semiconductors are plausible materials for gas-sensing technologies. 1 In general, sensing methods based on bulk crystals rely on the interactions between their surface atoms and the environment. This principle implies that nanocrystals (NCs) 2,3 and other ...

Journal of Physics: Condensed Matter, 1997

We have performed ab initio pseudopotential calculations within the local density approximation t... more We have performed ab initio pseudopotential calculations within the local density approximation to investigate the structural phase transition of ZnTe under pressure. Zn 3d and Te 4d orbitals are treated as part of the valence states in order to describe the structural properties of ZnTe accurately. By calculating the total energy, atomic force, and stress tensors, we theoretically determine the structural phase transition of ZnTe from the zinc-blende (ZB) to the cinnabar to the distorted NaCl structure under increasing pressure. Calculational results are compared in detail with the recent experimental data obtained using angle-dispersive techniques and an image-plate detector. We also demonstrate that rotation of bonds toward lower-symmetry positions occurs at the critical pressure to relieve excessive strain. Detailed electronic structures of each phase are also presented.

Journal of Physics: Condensed Matter, 1998

We present the results of a theoretical study of the structural phase transformations of ZnS unde... more We present the results of a theoretical study of the structural phase transformations of ZnS under high pressure, using first-principles pseudopotential and full-potential linear muffin-tin orbital methods, in which the semicore Zn d electrons are treated as valence states. The zincblende, NaCl and cinnabar forms of ZnS have been considered. The structural properties and the band structures of these systems have also been studied. In the case of the FP-LMTO approach, an optimal choice of the empty spheres, atomic radii and filling percentage is introduced, which gives results in excellent agreement with those of the present pseudopotential method. It has been found that cinnabar phase is not a stable phase in ZnS under high pressure. The cinnabar phase is predicted to be a semiconductor with a direct band gap of about 3.6 eV.

Journal of Luminescence, 2002

We report here the first observation of photoluminescence from single CdSe quantum confined nanor... more We report here the first observation of photoluminescence from single CdSe quantum confined nanorods (quantum rods). Luminescence imaging spectra of individual rods were obtained for two samples, with average aspect ratio of 2 and 4, respectively. Typical room-temperature luminescence spectral line widths of the rods in both samples are less than 60 meV, which are about the same as that of high-quality CdSe/CdS core/shell single quantum dots. Single quantum rods also exhibit luminescence intermittence as observed in single-dot systems. r

Applied Physics Letters, 2014

Temperature-dependent photoluminescence (PL) study has been conducted in Ge1−xSnx films with Sn c... more Temperature-dependent photoluminescence (PL) study has been conducted in Ge1−xSnx films with Sn compositions of 0.9%, 3.2%, and 6.0% grown on Si. The competing between the direct and indirect bandgap transitions was clearly observed. The relative peak intensity of direct transition with respect to the indirect transition increases with an increase in temperature, indicating the direct transition dominates the PL at high temperature. Furthermore, as Sn composition increases, a progressive enhancement of direct transition was observed due to the reduction of direct-indirect valley separation, which experimentally confirms that the Ge1−xSnx could become the group IV-based direct bandgap material grown on Si by increasing the Sn content.

CLEO: 2015, 2015

Temperature-dependent electroluminescence from a double heterostructure n-Ge/i-Ge<sub>0.94&... more Temperature-dependent electroluminescence from a double heterostructure n-Ge/i-Ge_0.94Sn_0.06/p-Ge LED was studied. The peak position of EL spectra showed a blue-shift as the temperature decreased. A maximum emission power of 7 mW was obtained under the current density of 800 A/cm².

11th International Conference on Group IV Photonics (GFP), 2014

The Ge/Ge0.94Sn0.06/Ge double heterostructure was grown on a Si substrate via chemical vapor depo... more The Ge/Ge0.94Sn0.06/Ge double heterostructure was grown on a Si substrate via chemical vapor deposition (CVD). The temperature and pump power-dependent photoluminescence (PL) were investigated and the enhanced direct transition at intense pump power was observed.

Applied Physics Letters, 2014

Material and optical characterizations have been conducted for epitaxially grown Ge1−xSnx thin fi... more Material and optical characterizations have been conducted for epitaxially grown Ge1−xSnx thin films on Si with Sn composition up to 10%. A direct bandgap Ge0.9Sn0.1 alloy has been identified by temperature-dependent photoluminescence (PL) study based on the single peak spectrum and the narrow line-width. Room temperature PL emission as long as 2230 nm has also been observed from the same sample.

2014 IEEE Photonics Conference, 2014

The interdigitated electrodes were integrated on Ge0.93Sn0.07/Ge heterostructure photoconductive ... more The interdigitated electrodes were integrated on Ge0.93Sn0.07/Ge heterostructure photoconductive detectors. Photoresponse extending to 2.2 μm was achieved, and the enhanced responsivity with reduced spacing between interdigitated electrodes was observed at room temperature.

Journal of Electronic Materials, 2014

High-quality compressive-strained Ge 1Àx Sn x /Ge films have been deposited on Si(001) substrate ... more High-quality compressive-strained Ge 1Àx Sn x /Ge films have been deposited on Si(001) substrate using a mainstream commercial chemical vapor deposition reactor. The growth temperature was kept below 450°C to be compatible with Si complementary metal-oxide-semiconductor processes. Germanium tin (Ge 1Àx Sn x) layers were grown with different Sn composition ranging from 0.9% to 7%. Material characterizations, such as secondary-ion mass spectrometry, Rutherford backscattering spectrometry, and x-ray diffraction analysis, show stable Sn incorporation in the Ge lattice. Comparison of the Sn mole fractions obtained using these methods shows that the bowing factor of 0.166 nm (in Vegard's law) is in close agreement with other experimental data. High-resolution transmission electron microscopy and atomic force microscopy results show that the films have started to relax through the formation of misfit and threading dislocations. Raman spectroscopy, ellipsometry, and photoluminescence (PL) techniques are used to study the structural and optical properties of the films. Room-temperature PL of the films shows that 7% Sn incorporation in the Ge lattice results in a decrease in the direct bandgap of Ge from 0.8 eV to 0.56 eV.

CLEO: 2014, 2014

ABSTRACT Photoluminescence (PL) from Ge1-xSnx grown on Si by CVD was investigated for Sn composit... more ABSTRACT Photoluminescence (PL) from Ge1-xSnx grown on Si by CVD was investigated for Sn composition of 0.9, 3.2, 6, and 7%, respectively. The direct and indirect band transitions were analyzed at different temperatures.

Bulletin of the American Physical Society, 2016

Submitted for the MAR16 Meeting of The American Physical Society Hybrid DFT calculations of the b... more Submitted for the MAR16 Meeting of The American Physical Society Hybrid DFT calculations of the band structure of alpha-Sn ERIN DUPAY1, LUCAS DOMULEVICZ2, HENRY CASTEJON3, AMJAD NAZZAL4, Wilkes Univ — The electronic properties of bulk alpha-tin were revisited using first principles. The band structure, in addition to other properties, such as the absorption spectrum and density of states, were calculated using Density Functional Theory and the HSE06 hybrid functional. The direct and indirect band gaps obtained from these calculations are in better agreement with experimental results than previously reported calculations. 1Graduate Student 2Undergraduate Student 3Faculty 4faculty Amjad Nazzal Wilkes Univ Date submitted: 06 Nov 2015 Electronic form version 1.4

Technical Digest. Summaries of papers presented at the Quantum Electronics and Laser Science Conference. Postconference Technical Digest (IEEE Cat. No.01CH37172)

Summary form only given. Recently, it has been demonstrated that the shape of CdSe nanocrystals c... more Summary form only given. Recently, it has been demonstrated that the shape of CdSe nanocrystals can be manipulated by controlling the growth kinetics (Peng et al, Nature, vol. 404, p. 59, 2000). The resulting nanostructures can be from a nearly spherical morphology to a rod-like one. The quantum confined nano-rods (quantum rods) can grow up to 200 nm long with an aspect ratio of up to 50. The successful growth of these rod- and wire-like structures provides a testing ground for studying the shape-dependent electronic and optical properties of nanocrystals and the quantum confinement effects in one-dimensional (1D) and quasi-1D regime, and in comparison with much characterized zero-dimensional (OD) quantum-dot system. Consequently, studies of quantum-rod system will explore another dimension for device applications of colloidal nanocrystals. In this paper, we report the optical studies of single CdSe quantum rods using far-field microscopic techniques.

ABSTRACT Ge 1−xSnx thin films with Sn composition up to 7% were epitaxially grown by chemical vap... more ABSTRACT Ge 1−xSnx thin films with Sn composition up to 7% were epitaxially grown by chemical vapor deposition on silicon. Temperature-dependent photoluminescence was investigated and the peaks corresponding to the direct and indirect transitions were observed in a wavelength range from 1.6 to 2.2 μm. The exact peak positions obtained from Gaussian fitting were fitted with an empirical temperature dependent band-gap equation (Varshni relationship). The separation between direct and indirect peaks was equal to 0.012 eV for GeSn thin film with 7% Sn content at room temperature. This observation indicates that the indirect-to-direct crossover would take place at slightly higher Sn compositions.

Applied Physics Letters, 2014

The Journal of Physical Chemistry B, 2004

We report our systematic studies of the environmental effects on the photoluminescence (PL) from ... more We report our systematic studies of the environmental effects on the photoluminescence (PL) from colloidal CdSe nanocrystals (NCs) embedded in polymer thin films. The highly luminescent bare-core CdSe NCs were significantly more robust than the core/shell CdSe/ZnS NCs against photoannealing under inert environments, while the core/shell NCs are more resistant to photooxidation. For the case of bare-core NCs, we show the importance of the initial photoactivation as the proper treatment for subsequent studies, a step that is basically irrelevant in the case of core/shell NCs. By measuring the PL wavelength shift, PL line width, and PL intensity, we investigated the dynamic changes of the emission properties of these NCs under different environments, including argon, oxygen, air, water vapor, and wet oxygen, and under different excitation conductions to reveal the photoinduced nature of the interactions between the nanocrystal surface and the environment. Mechanisms related to photoactivation, photooxidation, and PL enhancement are briefly discussed.

CLEO: 2014, 2014

GeSn/Ge heterostructure microdisks integrated on Si were fabricated. The quality of material grow... more GeSn/Ge heterostructure microdisks integrated on Si were fabricated. The quality of material grown by CVD was investigated and the photoluminescence spectrum was measured using a Ti:Sapphire laser as an excitation source under variable pump powers.

Physical Review B, 1995

... (7) (the so-called potential lineup)is extracted fromsimi-lar calculations for supercells con... more ... (7) (the so-called potential lineup)is extracted fromsimi-lar calculations for supercells containing thick slabs of the two materials. The macroscopic averaging used to calculate V„, was performed using the moving-slab averaging technique of Baldereschi, Baroni, and Resta. ...

Physical Review B, 2001

Excitation and emission spectra of CdSe single quantum rods with aspect ratios of 2 and 4 were in... more Excitation and emission spectra of CdSe single quantum rods with aspect ratios of 2 and 4 were investigated by far-field microscopic technique. Typical spectral linewidths of the rods are less than 60 meV at room temperature. Both excitation and emission of the single rods exhibit ...

Physical Review B, 2005

Organic-inorganic hybrid semiconductor ZnSe(C2H8N2)1/2 under hydrostatic pressure is studied usin... more Organic-inorganic hybrid semiconductor ZnSe(C2H8N2)1/2 under hydrostatic pressure is studied using a first-principles pseudopotential method with mixed-basis set, aimed at understanding its structural, mechanical, and electronic properties. The bulk modulus of the hybrid is determined to be 35.3GPa , which is considerably smaller than that of bulk ZnSe and, in fact, smaller than most known tetrahedral bulk semiconductors. We find that, when the hybrid is exposed to pressure, the chemical bonds of the inorganic constituent, not those of the organic constituent, are significantly compressed. This is important and allows the band-edge electronic properties of hybrid chalcogenides to be effectively tuned by applying pressure, since these properties can be substantially modified only by changing the inorganic Zn-Se bonds. Our calculations further demonstrate that the pressure dependence of the band gap in hybrid semiconductor shows an unusual nonlinearity, with a bowing coefficient that is more than one order of magnitude larger than in bulk ZnSe. Moreover, our results reveal that the in-plane electron mobility mass is notably small (me*˜0.27) and remains unchanged over a wide range of pressure. The hybrids will thus continue to maintain a fast electron mobility when they are under mechanical loading. However, and interestingly, the in-plane hole mass along the x and y direction is predicted to undergo at 2.14GPa a dramatic change from 0.35 to 2.2 and from 2.0 to 0.24, respectively. A pressure-induced isostructural phase transition is found to be responsible for this behavior of hole mass.

Nano Letters, 2003

Bulk and thin-film semiconductors are plausible materials for gas-sensing technologies. 1 In gene... more Bulk and thin-film semiconductors are plausible materials for gas-sensing technologies. 1 In general, sensing methods based on bulk crystals rely on the interactions between their surface atoms and the environment. This principle implies that nanocrystals (NCs) 2,3 and other ...

Journal of Physics: Condensed Matter, 1997

We have performed ab initio pseudopotential calculations within the local density approximation t... more We have performed ab initio pseudopotential calculations within the local density approximation to investigate the structural phase transition of ZnTe under pressure. Zn 3d and Te 4d orbitals are treated as part of the valence states in order to describe the structural properties of ZnTe accurately. By calculating the total energy, atomic force, and stress tensors, we theoretically determine the structural phase transition of ZnTe from the zinc-blende (ZB) to the cinnabar to the distorted NaCl structure under increasing pressure. Calculational results are compared in detail with the recent experimental data obtained using angle-dispersive techniques and an image-plate detector. We also demonstrate that rotation of bonds toward lower-symmetry positions occurs at the critical pressure to relieve excessive strain. Detailed electronic structures of each phase are also presented.

Journal of Physics: Condensed Matter, 1998

We present the results of a theoretical study of the structural phase transformations of ZnS unde... more We present the results of a theoretical study of the structural phase transformations of ZnS under high pressure, using first-principles pseudopotential and full-potential linear muffin-tin orbital methods, in which the semicore Zn d electrons are treated as valence states. The zincblende, NaCl and cinnabar forms of ZnS have been considered. The structural properties and the band structures of these systems have also been studied. In the case of the FP-LMTO approach, an optimal choice of the empty spheres, atomic radii and filling percentage is introduced, which gives results in excellent agreement with those of the present pseudopotential method. It has been found that cinnabar phase is not a stable phase in ZnS under high pressure. The cinnabar phase is predicted to be a semiconductor with a direct band gap of about 3.6 eV.

Journal of Luminescence, 2002

We report here the first observation of photoluminescence from single CdSe quantum confined nanor... more We report here the first observation of photoluminescence from single CdSe quantum confined nanorods (quantum rods). Luminescence imaging spectra of individual rods were obtained for two samples, with average aspect ratio of 2 and 4, respectively. Typical room-temperature luminescence spectral line widths of the rods in both samples are less than 60 meV, which are about the same as that of high-quality CdSe/CdS core/shell single quantum dots. Single quantum rods also exhibit luminescence intermittence as observed in single-dot systems. r