Xiaoman Duan | Massachusetts Institute of Technology (MIT) (original) (raw)

Papers by Xiaoman Duan

MRS Proceedings, 2000

The Si/SiO2 interface is attracting new interest as gate dielectrics in MOS devices become ultra ... more The Si/SiO2 interface is attracting new interest as gate dielectrics in MOS devices become ultra thin. In this paper, the impact of pre-gate cleaning on the morphology of the Si/SiO2 interface and the electrical performance of CMOS gate oxides has been systematically investigated. Using the High-Resolution Transmission Electron Microscopy (HRTEM) technique, we observed the Si/SiO2 interface at an atomic level. We have found a direct experimental relationship between the pre-gate cleaning scheme, Si/SiO2 interface morphology, and the electrical properties of CMOS gate oxides. When the ratio of H2O2:NH4OH ≥ 1.45, the roughness of the Si/SiO2 interface was dramatically improved, which, in turn, increased the Charge-to-Breakdown to an ideal value.

MRS Proceedings, 1996

We have fabricated Si:Er films by ion implantation and ultra-high vacuum chemical vapor depositio... more We have fabricated Si:Er films by ion implantation and ultra-high vacuum chemical vapor deposition (UHV-CVD). The energy of the ion implantation was varied from 200 keV to 4.5 MeV. Oxygen was co-implanted to overlap the erbium profile. At implant energies of 400 keV, we found that the luminescence was optimized at a lower annealing temperature (800° C, 30 minutes) than that needed for the 4.5 MeV implant (900°C, 30 minutes). The light intensity per erbium atom is critically dependent on the implantation energy. However, spreading resistance measurements show that the donor activity of the implanted erbium is independent of energy. We have correlated the donor activity with quantum efficiency by varying the donor spatial distribution and concentration through post implantation heat treatments.For the UHV-CVD grown Si:Er films, two erbium metallorganic precursors, Er(TMHD)3 and Er(FOD)3. have been used for growths from 550–620°C. The thickness of the erbium layers are similar to that ...

Applied Physics Letters, 2006

... Si solar cells integrated with the textured photonic crystal back reflector were designed and... more ... Si solar cells integrated with the textured photonic crystal back reflector were designed and fabricated. External quantum efficiency was significantly improved between the wavelengths of 1000 and (enhancement up to 135 times), and the overall power conversion efficiency ...

MRS Proceedings, 2014

ABSTRACTMonolayers of arrays of periodic polystyrene (PS) spheres are designed to couple onto the... more ABSTRACTMonolayers of arrays of periodic polystyrene (PS) spheres are designed to couple onto the surface of cerium-doped lutetium-yttrium oxyorthosilicate scintillator to improve the light extraction efficiency. The enhancement of extraction efficiency up to 38% relative to the reference case without polystyrene spheres is achieved. Combining with the simulation for the transmission as well as its dispersion relation, detailed analysis of the effect of whispering gallery modes and diffraction on the extraction mechanism are given. As a result, the optimal diameter of 414 nm is obtained based on a trade-off between the transmission loss and the diffraction enhancement.

MRS Proceedings, 2014

ABSTRACTWe present results of theoretical and experimental studies of whispering-gallery modes in... more ABSTRACTWe present results of theoretical and experimental studies of whispering-gallery modes in optical microdisk resonators interacting with subwavelength dielectric particles. We predict theoretically and confirm by direct observations that, contrary to the generally accepted models, both peaks of the particle-induced doublet of resonances are red shifted with respect to the position of the initial resonance.

Nanostructure Science and Technology, 2009

The quest to develop an efficient Si-based light emitter has stimulated research worldwide. Among... more The quest to develop an efficient Si-based light emitter has stimulated research worldwide. Among the several approaches being considered, enhancing the probability of light emission through the use of Si nanocrystals embedded in SiO2 shows considerable promise due to the demonstration of efficient room temperature light emission and optical gain. In this chapter, we compare the nucleation, light emission, and

MRS Proceedings, 2013

ABSTRACTAntireflection with broadband and wide angle properties is important for a wide range of ... more ABSTRACTAntireflection with broadband and wide angle properties is important for a wide range of applications on photovoltaic cells and display. The SiOx shell layer provides a natural antireflection from air to the Si core absorption layer. In this work, we have demonstrated the random core-shell silicon nanowires with both broadband (from 400nm to 900nm) and wide angle (from normal incidence to 60°) antireflection characteristics within AM1.5 solar spectrum. The graded index structure from the randomly oriented core-shell (Air/SiOx/Si) nanowires may provide a potential avenue to realize a broadband and wide angle antireflection layer.

MRS Proceedings, 2013

ABSTRACTWe have improved bio-inspired Moth eye nanostructures to enhance the scintillator materia... more ABSTRACTWe have improved bio-inspired Moth eye nanostructures to enhance the scintillator materials external quantum efficiency significantly. As a proof of concept, we have demonstrated very high light output efficiency enhancement for Lu2SiO5:Ce3+ (LSO:Ce) film in large area. The X-ray mammographic instrument was employed to demonstrate the light output enhancement of the Lu2SiO5:Ce thin film with bio-inspired Moth eye-like nano photonic structures. Our work could be extended to other thin film scintillator materials and is promising to achieve lower patient dose, higher resolution image of human organs and even smaller scale medical imaging.

Integrated Photonics Research, 2002

Materials Science and Engineering: B, 2001

Applied Physics Letters, 2004

Aperiodic one-dimensional Thue–Morse (T–M) multilayer structures have been fabricated in order to... more Aperiodic one-dimensional Thue–Morse (T–M) multilayer structures have been fabricated in order to investigate both the band gap properties with respect to the system size (band gap scaling) and the omnidirectional reflectance at the fundamental optical band gap. ...

MRS Proceedings, 2004

Aperiodic one dimensional Si/SiO2 Thue-Morse (T-M) multilayer structures have been fabricated, fo... more Aperiodic one dimensional Si/SiO2 Thue-Morse (T-M) multilayer structures have been fabricated, for the first time, in order to investigate both the band-gap behavior, with respect to the system size (band-gap scaling), and the omnidirectional reflectance of the fundamental optical band-gap. Variable angle reflectance data have experimentally demonstrated a large reflectance band-gap in the optical spectrum of a T-M quasicrystal, in agreement with transfer matrix simulations. We have explained the physical origin of the T-M omnidirectional band-gap as a result of periodic spatial correlations in the self-similar T-M structure, as revealed by Fourier Transform and Wavelet analysis. The unprecedented degree of structural flexibility showed by T-M systems can provide an attractive alternative to photonic crystals for the fabrication of photonic devices.

Proceedings of …, 1998

Research in erbium-doped silicon (Si: Er) is discussed in light of our effort to improve the lumi... more Research in erbium-doped silicon (Si: Er) is discussed in light of our effort to improve the luminescence performance of our LEDs and to demonstrate an integration scheme for a microphotonic clock distribution system. Excitation from Si: Er can occur int ow ways:(1) ...

ABSTRACTWe have successfully developed a new light-trapping scheme for solar cells that can enhan... more ABSTRACTWe have successfully developed a new light-trapping scheme for solar cells that can enhance the optical path length by more than 104 times using a textured photonic crystal structure as a backside reflector. Top-contacted crystalline Si solar cells integrated with the new back reflector were designed, fabricated and characterized. Both external quantum efficiency and power conversion efficiency of the cells have shown significant improvement due to the path length enhancement furnished by the new back reflector despite of the 675 um thick wafers and relatively short minority carrier diffusion length.

International Journal of Powder Metallurgy, 1993

Two spray deposited, high strength 7150 aluminum alloys, one with increased nominal levels of iro... more Two spray deposited, high strength 7150 aluminum alloys, one with increased nominal levels of iron and silicon and the other of standard composition, were prepared by rapid solidification, liquid dynamic compaction (LDC). Spray deposition for this study was done with a circular ultrasonic gas atomization nozzle (USGA). The as-deposited materials showed high densities (96 ± 3%) and fine (< 20mm) equiaxed microstructures with very low alloy segregation and a very fine, uniform distribution of excess phases, the predominant one being metastable Al 6 Fe. No elemental silicon, Mg 2 Si or any other excess phases were detected in the as-deposited alloys

MRS Proceedings, 1996

A systematic study of defects in the Er/O implanted silicon was conducted using TEM, HRTEM and SI... more A systematic study of defects in the Er/O implanted silicon was conducted using TEM, HRTEM and SIMS. Defect-free material was obtained after the annealing of 400 keV Er+ implanted (100)Si. In sharp contrast, several forms of secondary defects consisting of dislocations, dislocation loops and precipitates were induced upon annealing at different temperatures in the 4.5 MeV implanted (100)Si sample. The isothermal evolution of the defects and reactions between dopants and defects were studied. Oxygen tends to segregate into the dislocation loop zones, where platelet precipitates with habit planes of {111} were found. Following dissociation of oxygen and erbium, plate-like Er precipitates were generated, which are most likely ErSi2 with a habit plane of {111}

… on Lasers and …, 2010

... Institute of Microsystems and Information Technology, Shanghai, China 200050 3NYU and CUNY Gr... more ... Institute of Microsystems and Information Technology, Shanghai, China 200050 3NYU and CUNY Graduate Center, NYC, NY 10314 4yys@alum.mit.edu Abstract: we present the design, processing and characterization of Si-on-insulator thin film solar cells integrated with ...

Journal of applied …, 1996

Photonic integrated circuits in silicon require waveguiding through a material compatible with si... more Photonic integrated circuits in silicon require waveguiding through a material compatible with silicon very large scale integrated circuit technology. Polycrystalline silicon (poly-Si), with a high index of refraction compared to SiO2 and air, is an ideal candidate for use in silicon ...

Two spray deposited, high strength 7150 aluminum alloys, one with increased nominal levels of iro... more Two spray deposited, high strength 7150 aluminum alloys, one with increased nominal levels of iron and silicon and the other of standard composition, were prepared by rapid solidification, liquid dynamic compaction (LDC). Spray deposition for this study was done with a circular ultrasonic gas atomization nozzle (USGA). The as-deposited materials showed high densities (96±3%) and fine (<20mm) equiaxed microstructures with very low alloy segregation and a very fine, uniform distribution of excess phases, the predominant one being metastable Al6Fe. No elemental silicon, Mg2Si or any other excess phases were detected in the as-deposited alloys. The deposits were hot rolled for full densification and further structural refinement, and were given standard T6 treatments prior to room temperature tensile testing. Results show that the 7150 alloy with 0.5w/o Fe and 0.4w/o Si can be produced by LDC processing with excellent tensile properties: 0.2% Y.S.: 480 - 570MPa (68 - 81ksi), UTS: 545...

Science and technology of rapid …, 1995

Xiaoman Duan, Ali Farah, Ibrahim Ucok, Nicholas J Grant Science and technology of rapid solidific... more Xiaoman Duan, Ali Farah, Ibrahim Ucok, Nicholas J Grant Science and technology of rapid solidification and processing, 205-216, 1995. Liquid dynamic compaction (LDC) was used to develop rapidly solidified 2024 aluminum alloys modified with small additions of zirconium. ...

MRS Proceedings, 2000

The Si/SiO2 interface is attracting new interest as gate dielectrics in MOS devices become ultra ... more The Si/SiO2 interface is attracting new interest as gate dielectrics in MOS devices become ultra thin. In this paper, the impact of pre-gate cleaning on the morphology of the Si/SiO2 interface and the electrical performance of CMOS gate oxides has been systematically investigated. Using the High-Resolution Transmission Electron Microscopy (HRTEM) technique, we observed the Si/SiO2 interface at an atomic level. We have found a direct experimental relationship between the pre-gate cleaning scheme, Si/SiO2 interface morphology, and the electrical properties of CMOS gate oxides. When the ratio of H2O2:NH4OH ≥ 1.45, the roughness of the Si/SiO2 interface was dramatically improved, which, in turn, increased the Charge-to-Breakdown to an ideal value.

MRS Proceedings, 1996

We have fabricated Si:Er films by ion implantation and ultra-high vacuum chemical vapor depositio... more We have fabricated Si:Er films by ion implantation and ultra-high vacuum chemical vapor deposition (UHV-CVD). The energy of the ion implantation was varied from 200 keV to 4.5 MeV. Oxygen was co-implanted to overlap the erbium profile. At implant energies of 400 keV, we found that the luminescence was optimized at a lower annealing temperature (800° C, 30 minutes) than that needed for the 4.5 MeV implant (900°C, 30 minutes). The light intensity per erbium atom is critically dependent on the implantation energy. However, spreading resistance measurements show that the donor activity of the implanted erbium is independent of energy. We have correlated the donor activity with quantum efficiency by varying the donor spatial distribution and concentration through post implantation heat treatments.For the UHV-CVD grown Si:Er films, two erbium metallorganic precursors, Er(TMHD)3 and Er(FOD)3. have been used for growths from 550–620°C. The thickness of the erbium layers are similar to that ...

Applied Physics Letters, 2006

... Si solar cells integrated with the textured photonic crystal back reflector were designed and... more ... Si solar cells integrated with the textured photonic crystal back reflector were designed and fabricated. External quantum efficiency was significantly improved between the wavelengths of 1000 and (enhancement up to 135 times), and the overall power conversion efficiency ...

MRS Proceedings, 2014

ABSTRACTMonolayers of arrays of periodic polystyrene (PS) spheres are designed to couple onto the... more ABSTRACTMonolayers of arrays of periodic polystyrene (PS) spheres are designed to couple onto the surface of cerium-doped lutetium-yttrium oxyorthosilicate scintillator to improve the light extraction efficiency. The enhancement of extraction efficiency up to 38% relative to the reference case without polystyrene spheres is achieved. Combining with the simulation for the transmission as well as its dispersion relation, detailed analysis of the effect of whispering gallery modes and diffraction on the extraction mechanism are given. As a result, the optimal diameter of 414 nm is obtained based on a trade-off between the transmission loss and the diffraction enhancement.

MRS Proceedings, 2014

ABSTRACTWe present results of theoretical and experimental studies of whispering-gallery modes in... more ABSTRACTWe present results of theoretical and experimental studies of whispering-gallery modes in optical microdisk resonators interacting with subwavelength dielectric particles. We predict theoretically and confirm by direct observations that, contrary to the generally accepted models, both peaks of the particle-induced doublet of resonances are red shifted with respect to the position of the initial resonance.

Nanostructure Science and Technology, 2009

The quest to develop an efficient Si-based light emitter has stimulated research worldwide. Among... more The quest to develop an efficient Si-based light emitter has stimulated research worldwide. Among the several approaches being considered, enhancing the probability of light emission through the use of Si nanocrystals embedded in SiO2 shows considerable promise due to the demonstration of efficient room temperature light emission and optical gain. In this chapter, we compare the nucleation, light emission, and

MRS Proceedings, 2013

ABSTRACTAntireflection with broadband and wide angle properties is important for a wide range of ... more ABSTRACTAntireflection with broadband and wide angle properties is important for a wide range of applications on photovoltaic cells and display. The SiOx shell layer provides a natural antireflection from air to the Si core absorption layer. In this work, we have demonstrated the random core-shell silicon nanowires with both broadband (from 400nm to 900nm) and wide angle (from normal incidence to 60°) antireflection characteristics within AM1.5 solar spectrum. The graded index structure from the randomly oriented core-shell (Air/SiOx/Si) nanowires may provide a potential avenue to realize a broadband and wide angle antireflection layer.

MRS Proceedings, 2013

ABSTRACTWe have improved bio-inspired Moth eye nanostructures to enhance the scintillator materia... more ABSTRACTWe have improved bio-inspired Moth eye nanostructures to enhance the scintillator materials external quantum efficiency significantly. As a proof of concept, we have demonstrated very high light output efficiency enhancement for Lu2SiO5:Ce3+ (LSO:Ce) film in large area. The X-ray mammographic instrument was employed to demonstrate the light output enhancement of the Lu2SiO5:Ce thin film with bio-inspired Moth eye-like nano photonic structures. Our work could be extended to other thin film scintillator materials and is promising to achieve lower patient dose, higher resolution image of human organs and even smaller scale medical imaging.

Integrated Photonics Research, 2002

Materials Science and Engineering: B, 2001

Applied Physics Letters, 2004

Aperiodic one-dimensional Thue–Morse (T–M) multilayer structures have been fabricated in order to... more Aperiodic one-dimensional Thue–Morse (T–M) multilayer structures have been fabricated in order to investigate both the band gap properties with respect to the system size (band gap scaling) and the omnidirectional reflectance at the fundamental optical band gap. ...

MRS Proceedings, 2004

Aperiodic one dimensional Si/SiO2 Thue-Morse (T-M) multilayer structures have been fabricated, fo... more Aperiodic one dimensional Si/SiO2 Thue-Morse (T-M) multilayer structures have been fabricated, for the first time, in order to investigate both the band-gap behavior, with respect to the system size (band-gap scaling), and the omnidirectional reflectance of the fundamental optical band-gap. Variable angle reflectance data have experimentally demonstrated a large reflectance band-gap in the optical spectrum of a T-M quasicrystal, in agreement with transfer matrix simulations. We have explained the physical origin of the T-M omnidirectional band-gap as a result of periodic spatial correlations in the self-similar T-M structure, as revealed by Fourier Transform and Wavelet analysis. The unprecedented degree of structural flexibility showed by T-M systems can provide an attractive alternative to photonic crystals for the fabrication of photonic devices.

Proceedings of …, 1998

Research in erbium-doped silicon (Si: Er) is discussed in light of our effort to improve the lumi... more Research in erbium-doped silicon (Si: Er) is discussed in light of our effort to improve the luminescence performance of our LEDs and to demonstrate an integration scheme for a microphotonic clock distribution system. Excitation from Si: Er can occur int ow ways:(1) ...

ABSTRACTWe have successfully developed a new light-trapping scheme for solar cells that can enhan... more ABSTRACTWe have successfully developed a new light-trapping scheme for solar cells that can enhance the optical path length by more than 104 times using a textured photonic crystal structure as a backside reflector. Top-contacted crystalline Si solar cells integrated with the new back reflector were designed, fabricated and characterized. Both external quantum efficiency and power conversion efficiency of the cells have shown significant improvement due to the path length enhancement furnished by the new back reflector despite of the 675 um thick wafers and relatively short minority carrier diffusion length.

International Journal of Powder Metallurgy, 1993

Two spray deposited, high strength 7150 aluminum alloys, one with increased nominal levels of iro... more Two spray deposited, high strength 7150 aluminum alloys, one with increased nominal levels of iron and silicon and the other of standard composition, were prepared by rapid solidification, liquid dynamic compaction (LDC). Spray deposition for this study was done with a circular ultrasonic gas atomization nozzle (USGA). The as-deposited materials showed high densities (96 ± 3%) and fine (< 20mm) equiaxed microstructures with very low alloy segregation and a very fine, uniform distribution of excess phases, the predominant one being metastable Al 6 Fe. No elemental silicon, Mg 2 Si or any other excess phases were detected in the as-deposited alloys

MRS Proceedings, 1996

A systematic study of defects in the Er/O implanted silicon was conducted using TEM, HRTEM and SI... more A systematic study of defects in the Er/O implanted silicon was conducted using TEM, HRTEM and SIMS. Defect-free material was obtained after the annealing of 400 keV Er+ implanted (100)Si. In sharp contrast, several forms of secondary defects consisting of dislocations, dislocation loops and precipitates were induced upon annealing at different temperatures in the 4.5 MeV implanted (100)Si sample. The isothermal evolution of the defects and reactions between dopants and defects were studied. Oxygen tends to segregate into the dislocation loop zones, where platelet precipitates with habit planes of {111} were found. Following dissociation of oxygen and erbium, plate-like Er precipitates were generated, which are most likely ErSi2 with a habit plane of {111}

… on Lasers and …, 2010

... Institute of Microsystems and Information Technology, Shanghai, China 200050 3NYU and CUNY Gr... more ... Institute of Microsystems and Information Technology, Shanghai, China 200050 3NYU and CUNY Graduate Center, NYC, NY 10314 4yys@alum.mit.edu Abstract: we present the design, processing and characterization of Si-on-insulator thin film solar cells integrated with ...

Journal of applied …, 1996

Photonic integrated circuits in silicon require waveguiding through a material compatible with si... more Photonic integrated circuits in silicon require waveguiding through a material compatible with silicon very large scale integrated circuit technology. Polycrystalline silicon (poly-Si), with a high index of refraction compared to SiO2 and air, is an ideal candidate for use in silicon ...

Two spray deposited, high strength 7150 aluminum alloys, one with increased nominal levels of iro... more Two spray deposited, high strength 7150 aluminum alloys, one with increased nominal levels of iron and silicon and the other of standard composition, were prepared by rapid solidification, liquid dynamic compaction (LDC). Spray deposition for this study was done with a circular ultrasonic gas atomization nozzle (USGA). The as-deposited materials showed high densities (96±3%) and fine (<20mm) equiaxed microstructures with very low alloy segregation and a very fine, uniform distribution of excess phases, the predominant one being metastable Al6Fe. No elemental silicon, Mg2Si or any other excess phases were detected in the as-deposited alloys. The deposits were hot rolled for full densification and further structural refinement, and were given standard T6 treatments prior to room temperature tensile testing. Results show that the 7150 alloy with 0.5w/o Fe and 0.4w/o Si can be produced by LDC processing with excellent tensile properties: 0.2% Y.S.: 480 - 570MPa (68 - 81ksi), UTS: 545...

Science and technology of rapid …, 1995

Xiaoman Duan, Ali Farah, Ibrahim Ucok, Nicholas J Grant Science and technology of rapid solidific... more Xiaoman Duan, Ali Farah, Ibrahim Ucok, Nicholas J Grant Science and technology of rapid solidification and processing, 205-216, 1995. Liquid dynamic compaction (LDC) was used to develop rapidly solidified 2024 aluminum alloys modified with small additions of zirconium. ...