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TCU DEPARTMENT of PHYSICS and ASTRONOMY

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TCU Box 298840
Fort Worth, TX 76129
Phone: (817) 257-7375
Fax: (817) 257-7742
Email:physics@tcu.edu

This page maintained
by Kaoru Yoshida

Spring 2005 Seminar Information

The Ninth Annual
Joseph Morgan Lecture
(General information on the Morgan Lecture)

Monday February 21, 2005 at 7:30 p.m.
Lecture Hall 1, Sid Richardson Building
(Map for locating the Sid Richardson Building)

Refreshments will be served following the lecture

Dr. Phil Plait

httpWednesday, January 17, 2007p://home.fnal.gov/%7Erocky/">

Biographical Information

Dr. Philip Plait is an internationally-renowned speaker, author, and astronomer based at Sonoma State University in California. He spent ten years working on Hubble Space Telescope data, including five years at NASA's Goddard Space Flight Center. He is the webmaster of the award-winning "Bad Astronomy" website (http://www.badastronomy.com), where he dispels myths and misconceptions about astronomy. This includes gaffes by news organizations, movies, and plain old urban legends that seem to get stuck in peoples' heads. His book, also called "Bad Astronomy", is currently in its fifth printing. He has given talks about Bad Astronomy across the country, as well as on radio and television.

``Mars Attacks''

Abstract

Myths and legends about the Red Planet have been around for as long as people have looked at the stars. More recently, these myths have taken a decidedly alien turn, with claims about a Face on Mars, cities, and even mass transit systems! Dr. Plait will discuss these myths and, using his trademark blend of science and humor, show just why they are wrong.

Dr. Plait will also give a colloqium on February 21 entitled:

"The NASA Education and Public Outreach Program at Sonoma State
University"

Monday February 21, 2005, at 1:00 p.m.
Sid Richardson Building Room 357

Abstract: Dr. Plait will discuss the NASA Education and Public Outreach (EPO) program at Sonoma State University. Sonoma State University is the lead EPO institute for three high-energy NASA satellites which investigate the Universe in X-rays and gamma rays (including Swift, which just launched in November 2004). The EPO group has developed a wide range of fun, standards-based activities to help educators teach science and math to their students. Dr. Plait will give an overview of the program, and talk about the challenges (that is, the problems) in developing educational materials, getting them into the students' hands, and making it fun and interesting at the same time

For directions to the Sid Richardson Building see map, or contact the TCU Department of Physics and Astronomy at 817-257-7375.

Contact person: Dr. Marcum

Friday February 25 at 1:00 p.m. in SWR 357

Pre-dissertation

Vincent Jobando
Department of Physics and Astronomy
TCU

Homogeneity and Physical Aging of Carbon Black Filled Polymer Composites

Refreshments and the Pre-dissertation Oral Examination will follow

Sponsor: Dr. Quarles

Monday March 7 at 4:00 p.m. in SWR 357
Refreshments served between 3:00 and 4:00 p.m. during informal discussions with our visitor

Dr. Rohit Prasankumar
Los Alamos National Laboratory

Ultrafast Mid-and-Far-Infrared Dynamics of Correlated Electron Materials and Semiconductor Nanostructures

Abstract:

Ultrafast optical spectroscopy has attained prominence in chemistry, biology, and condensed matter physics in recent years due to its ability to resolve dynamics in conventional metals and semiconductors at the fundamental timescales of electron and lattice motion. However, the application of ultrafast spectroscopy to materials of more contemporary interest is still in its infancy, especially in the mid-and-far-infrared (IR) spectral range. Therefore, the ability to probe the dynamics of these novel systems in the mid-and-far-infrared stands to reveal a great deal of new information that will increase understanding of their basic physics.

In this work, optical-pump, mid-IR/THz-probe experiments are performed on different correlated electron materials and semiconductor nanostructures, yielding information important both for knowledge of their basic physics as well as applications in spintronics and infrared detection. In our research on correlated electron materials, we used optical-pump mid-IR probe spectroscopy to investigate coupled charge-spin dynamics in the magnetoresistive pyrochlore Tl₂Mn₂O₇. We found that the temporal persistence of the photo-excited carrier density is strongly influenced by long range spin correlations for I<0.8T_c and short range spin correlations for T>1.4T_c. For 0.8 T_c<T<1.4 T_c, the excess carrier density persisted for >1.5 nanoseconds, indicating a self-consistent stabilizing interaction between the Mn⁴⁺ core spins and the photo-injected free carriers. Our results revealed the dominance of spin fluctuations in determining the transport properties in Tl₂Mn₂O₇. In addition, we performed optical-pump mid-IR probe measurements on the ferromagnetic (T_c~250 K) and charge-and-orbital-ordered (T_co~150 K) manganite Nd_0.5Sr_0.5MnO₃ as a function of temperature, probing at energies both above and below the optical gap. Our results in the ferromagnetic regime are consistent with previous ultrafast measurements on half-metallic manganites, while below T_co we observed striking changes in the dynamics, believed to be due to photo-induced melting of the charge-and-orbital ordered state.

Another focus of our research is the study of carrier dynamics in semiconductor nanostructures. We used optical-pump THz-probe spectroscopy to study carrier dynamics in self-assembled ErAs nanoislands embedded in GaAs and deposited in a superlattice structure. The superior control of material parameters available with these devices makes them an attractive alternative to current THz detectors. Measurements were performed at several pump fluences on samples with different superlattice periods, enabling a determination of the time-dependent conductivity. We obtained sub-picosecond carrier capture times, indicating the potential of these devices as time domain THz detectors. We also performed optical-pump mid-IR probe experiments on dots-in-a-well (DWELL) detectors, which consist of InAs quantum dots sandwiched between thin In_0.15Ga_0.85As quantum wells (QW) that are subsequently placed in a GaAs matrix. By using a pump pulse to excite carriers in the bulk GaAs layers and tuning the mid-IR probe wavelength resonant with the transitions in the quantum wells and dots, we can track the relaxation of carriers from the bulk GaAs into the InGaAs quantum wells and finally into the InAs quantum dots. This enables us to track carrier relaxation from three to two to zero dimensions for the first time, to the best of our knowledge. In conclusion, our research into time-resolved mid-and-far-infrared dynamics in semiconductor nanostructures and correlated electron materials demonstrates the utility of ultrafast optical spectroscopy in studies of condensed matter systems, leading to advances in understanding their fundamental properties and optimizing them for different applications.

Sponsor: Dr. Rittby

Wednesday March 9 at 4:00 p.m. in SWR 357
Refreshments served between 3:00 and 4:00 p.m. during informal discussions with our visitor

Dr. Xuan Gao
Los Alamos National Laboratory

The 2D metallic state and metal-insulator transition: two decades of controversy

Abstract:

The celebrated scaling theory of localization predicts that there is no true metallic ground state for disordered Fermi liquids in two dimensions (2D) in zero magnetic field. However, experiments in early 1990’s have revealed an intriguing metallic state and metal-insulator transition in various low density 2D systems. For these systems, carriers are strongly correlated, as characterized by the large value of r_s, the ratio between Coulomb interaction energy and the Fermi energy E_F. It is currently being debated that if the strong correlations can stabilize a metallic non-Fermi liquid phase in 2D. In this talk I will present transport experiments on dilute 2D holes with r_s >20 in some world highest quality Gallium Arsenide (GaAs) quantum wells down to temperatures as low as 0.01K. We find that a small parallel magnetic field (B_||) suppresses the strength of the 2D metallicity without affecting its energy scale. In strong B_|| when the spins are all polarized, we observe a logarithmically diverging resistance of 2D holes at low T, as predicted by the scaling theory of localization, indicating the system is driven back to the Fermi liquid state. These experiments show that the 2D metallic behavior is closely related to the spins of the carriers. I will also discuss our recent observation of strongly enhanced hole-phonon coupling in dilute 2D GaAs hole system.

References: X. P.A. Gao et al., Phys. Rev. Lett., 88, 166803 (2002); ibid 89, 016801 (2002); ibid 93, 256402 (2004); cond-mat/0501686, to appear in PRL (2005).

Sponsor: Dr. Rittby

Monday March 21 at 4:00 p.m. in SWR 357
Refreshments served between 3:15 and 4:00 p.m. during informal discussions with our visitor

Dr. Yuri M. Strzhemechny
Center for Materials Research
The Ohio State University

Studies of Nanoscale Distribution of Defects in Semiconductors

Abstract:

Defects in semiconductors are often detrimental for their optoelectronic and transport properties. Understanding and control of those defects usually requires nanoscale sensitivity. For that purpose we employ a combination of experimental surface sentitive techniques such as Low Temperature Photoluminescence Spectroscopy, Depth-Dependent Cathodoluminescence Spectroscopy, X-Ray Photoelectron Spectroscopy, Auger Electron Spectroscopy, Secondary Ion Mass Spectrometry, and Secondary Electron Microscopy. To illustrate the power of those techniques, we report some of our recent results for single-crystalline ZnO and polycrystalline Cu(In,Ga)Se₂ processed with remote inductively-coupled plasmas.

Sponsor: Dr. Zerda

Wednesday March 23 at 4:00 p.m. in SWR 357
Refreshments served between 3:15 and 4:00 p.m. during informal discussions with our visitor

Dr. Ashutosh Tiwari
NSF Center for Advanced Materials & Smart Structures
Department of Materials Science & Engineering
North Carolina State University

Thin Films and Nanostructured Materials: Growth, Characterization and Multidisciplinary Applications

Abstract:

Nanoscience & Nanotechnology represents one of the hottest frontiers in Physical Sciences and Engineering. This is a multidisciplinary field and has tremendous applications in almost every field of Science & Technology. The word “Nanomaterials” is quite broad and involves a variety of structures ranging from zero dimensional atom clusters to three dimensional grain structures, from one dimensional superlattice structures to two-dimensional granular thin films. A common feature of all these systems is that they have at least one dimension in the nanometer range (1-100 nm). Confinement effects due to boundary conditions make “Nanostructured Materials” behave much differently than their bulk counterparts. In this talk, I will present some of my very exciting results related to these material systems. Major focus will be on following four topics: (i) Spintronics and Diluted Magnetic Semiconductors (ii) Nanodots for Magnetic Data Storage (iii) Ultra Sensitive Infrared Sensors (iv) Biocompatible Materials. Specifically, a new class of heteroepitaxial superlattice structure (La_0.7Sr_0.3MnO₃/ZnO) exhibiting giant magnetoresistance (GMR) at low magnetic fields (~100 Gauss) will be described. Experimental results about the growth and observation of room temperature ferromagnetism (RTF) in epitaxial thin films of transition metal (V, Mn, Co) doped ZnO and CeO₂ will be presented. These results will be compared with earlier theoretical predictions. This will be followed by our recent work on the synthesis of magnetic Nanodots for applications in ultrahigh density magnetic storage media. After this, fabrication of high quality NdNiO₃ based infrared sensors and their integration with Silicon substrate will be discussed. Finally, I will talk about some of our interesting results related to the synthesis of Silver doped Diamond like Carbon (DLC) films, which exhibit significant antimicrobial properties and act as excellent biocompatible materials.

Sponsor: Dr. Zerda

Tuesday March 29 at 4:00 p.m. in SWR 357
Refreshments served between 3:15 and 4:00 p.m. during informal discussions with our visitor

Dr. Ruihua Cheng
Materials Science Division and Center for Nanoscale Materials
Argonne National Laboratory

Properties of Magnetic Nanostructures Fabricated via Epitaxial Growth

Abstract:

Magnetic nanostructures are of great interests in recent years due to their technical applications as well as rich fundamental physics. While extensive progress has been made to understand magnetic films, our knowledge of one-dimensional (1D) and zero-dimensional (0D) ferromagnetism is limited. In this presentation, I will discuss the fabrication and characterization of low dimensional magnetic nanostructures, especially self-assembled magnetic nanodots on Ru(0001) substrates and nanowires on Pt(997) vicinal surface. Nanoscale phenomena such as dimensionality, domains and their interactions, and metastable states are explored by magnetic force microscopy (MFM), scanning tunneling microscopy (STM), magneto-optical Kerr effect (MOKE), spin polarized low energy electron microscopy (SPLEEM), and photoemission electron microscopy (PEEM). The shape, alignment and magnetic anisotropy of the self-assembled nanomagnets can be controlled by substrates modification. The potential application of nanostructures on nanoscale spin detection will be addressed as well.

Sponsor: Dr. Zerda

Thursday March 31 at 4:00 p.m. in SWR 357
Refreshments served between 3:15 and 4:00 p.m. during informal discussions with our visitor

Dr. Anatoliy Glushchenko
Liquid Crystal Institute
Kent State University

Controlling light by liquid crystals: recent frontiers

Abstract:

Liquid crystals are beautiful and still mysterious. I am fond of them for both reasons. My talk will introduce these fascinating materials and hopefully engage the audience to investigate further their intriguing science and applications.
We have known of the existence of liquid crystals for more than 100 years. Research in the field is inherently multidisciplinary, engaging researchers in physics, chemistry, optics, mechanics, and mathematical simulations. Understanding the liquid crystal phase is an inherently certain three-dimensional problem requiring not only the visualization of complex molecular structures but also how these molecules organize in a myriad of complex geometries. Over the last few decades, scientists have effectively exploited the unique properties of liquid crystals to produce increasingly sophisticated displays. Combining liquid crystals with other materials has led to a great number of scientific discoveries and the formulation of even more fascinating materials. A great example is liquid crystal / polymer dispersions. Their study is breathtaking, and their application is very diverse, from nano-structured photonic devices, microscopic adaptive and diffractive optical elements, and large light modulators used for beam steering and missile defense systems.

Sponsor: Dr. Zerda

Friday April 8 at 1:00 p.m. in SWR 357

Pre-dissertation

Michael Vick
Department of Physics and Astronomy
TCU

Probing the Concordance Cosmology with Galaxy Cluster Substructure

Refreshments and the Pre-dissertation Oral Examination will follow

Sponsor: Dr. Quarles

College of Science and Engineering
Student Research Symposium

Friday April 22

Wednesday April 27 at 3:30 p.m. in SWR 357

PHYS 50733 Colloquia

These are 15 minute presentations of projects that students have worked on in Dr. Marcum's PHYS 50733 class.

Billy Quarles - How comet morphology changes with solar system age

Cort Spellman - Using cross-correlation techniques to measure gravitational redshifts of white dwarf stars

Ryan Haygood - N-body simulations of interacting galaxies

George Peyton - A JAVA program to predict the light curves of occulting binary star systems

Department of Physics and Astronomy
TCU

Sponsor: Dr.Marcum

Friday April 29 at 1:00 p.m. in SWR 357

Pre-dissertation

Rafael Cardenas
Department of Physics and Astronomy
TCU

Experimental Advances in the Production of Carbon Clusters

Refreshments and the Pre-dissertation Oral Examination will follow

Sponsor: Dr. Graham


	TCU DEPARTMENT of PHYSICS and ASTRONOMY
Department Home Page College Home Page TCU Home Page my.tcu.edu TCU Library Undergraduate Program On-Line Ugrad Bulletin Graduate Program On-Line Grad Bulletin Brochure (PDF) Student Information REU Program Fall 2007 Courses Physics Tutoring Center Individual Tutors eCollege Faculty Adjunct Faculty Staff Graduate Students Research Areas Undergraduate Students SPS SERC TCU Institute of Mathematics, Science and Technology Education Seminars TCU Sigma Xi Directions to dept. TCU Box 298840 Fort Worth, TX 76129 Phone: (817) 257-7375 Fax: (817) 257-7742 Email:physics@tcu.edu This page maintained by Kaoru Yoshida	Spring 2005 Seminar Information The Ninth Annual Joseph Morgan Lecture (General information on the Morgan Lecture) Monday February 21, 2005 at 7:30 p.m. Lecture Hall 1, Sid Richardson Building (Map for locating the Sid Richardson Building) Refreshments will be served following the lecture Dr. Phil Plait httpWednesday, January 17, 2007p://home.fnal.gov/%7Erocky/"> Biographical Information Dr. Philip Plait is an internationally-renowned speaker, author, and astronomer based at Sonoma State University in California. He spent ten years working on Hubble Space Telescope data, including five years at NASA's Goddard Space Flight Center. He is the webmaster of the award-winning "Bad Astronomy" website (http://www.badastronomy.com), where he dispels myths and misconceptions about astronomy. This includes gaffes by news organizations, movies, and plain old urban legends that seem to get stuck in peoples' heads. His book, also called "Bad Astronomy", is currently in its fifth printing. He has given talks about Bad Astronomy across the country, as well as on radio and television. *``Mars Attacks''* Abstract Myths and legends about the Red Planet have been around for as long as people have looked at the stars. More recently, these myths have taken a decidedly alien turn, with claims about a Face on Mars, cities, and even mass transit systems! Dr. Plait will discuss these myths and, using his trademark blend of science and humor, show just why they are wrong. Dr. Plait will also give a colloqium on February 21 entitled: "The NASA Education and Public Outreach Program at Sonoma State University" Monday February 21, 2005, at 1:00 p.m. Sid Richardson Building Room 357 Abstract: Dr. Plait will discuss the NASA Education and Public Outreach (EPO) program at Sonoma State University. Sonoma State University is the lead EPO institute for three high-energy NASA satellites which investigate the Universe in X-rays and gamma rays (including Swift, which just launched in November 2004). The EPO group has developed a wide range of fun, standards-based activities to help educators teach science and math to their students. Dr. Plait will give an overview of the program, and talk about the challenges (that is, the problems) in developing educational materials, getting them into the students' hands, and making it fun and interesting at the same time For directions to the Sid Richardson Building see map, or contact the TCU Department of Physics and Astronomy at 817-257-7375. Contact person: Dr. Marcum Friday February 25 at 1:00 p.m. in SWR 357 Pre-dissertation Vincent Jobando Department of Physics and Astronomy TCU Homogeneity and Physical Aging of Carbon Black Filled Polymer Composites Refreshments and the Pre-dissertation Oral Examination will follow Sponsor: Dr. Quarles Monday March 7 at 4:00 p.m. in SWR 357 Refreshments served between 3:00 and 4:00 p.m. during informal discussions with our visitor Dr. Rohit Prasankumar Los Alamos National Laboratory Ultrafast Mid-and-Far-Infrared Dynamics of Correlated Electron Materials and Semiconductor Nanostructures Abstract: Ultrafast optical spectroscopy has attained prominence in chemistry, biology, and condensed matter physics in recent years due to its ability to resolve dynamics in conventional metals and semiconductors at the fundamental timescales of electron and lattice motion. However, the application of ultrafast spectroscopy to materials of more contemporary interest is still in its infancy, especially in the mid-and-far-infrared (IR) spectral range. Therefore, the ability to probe the dynamics of these novel systems in the mid-and-far-infrared stands to reveal a great deal of new information that will increase understanding of their basic physics. In this work, optical-pump, mid-IR/THz-probe experiments are performed on different correlated electron materials and semiconductor nanostructures, yielding information important both for knowledge of their basic physics as well as applications in spintronics and infrared detection. In our research on correlated electron materials, we used optical-pump mid-IR probe spectroscopy to investigate coupled charge-spin dynamics in the magnetoresistive pyrochlore Tl₂Mn₂O₇. We found that the temporal persistence of the photo-excited carrier density is strongly influenced by long range spin correlations for I<0.8T_c and short range spin correlations for T>1.4T_c. For 0.8 T_c<T<1.4 T_c, the excess carrier density persisted for >1.5 nanoseconds, indicating a self-consistent stabilizing interaction between the Mn⁴⁺ core spins and the photo-injected free carriers. Our results revealed the dominance of spin fluctuations in determining the transport properties in Tl₂Mn₂O₇. In addition, we performed optical-pump mid-IR probe measurements on the ferromagnetic (T_c~250 K) and charge-and-orbital-ordered (T_co~150 K) manganite Nd_0.5Sr_0.5MnO₃ as a function of temperature, probing at energies both above and below the optical gap. Our results in the ferromagnetic regime are consistent with previous ultrafast measurements on half-metallic manganites, while below T_co we observed striking changes in the dynamics, believed to be due to photo-induced melting of the charge-and-orbital ordered state. Another focus of our research is the study of carrier dynamics in semiconductor nanostructures. We used optical-pump THz-probe spectroscopy to study carrier dynamics in self-assembled ErAs nanoislands embedded in GaAs and deposited in a superlattice structure. The superior control of material parameters available with these devices makes them an attractive alternative to current THz detectors. Measurements were performed at several pump fluences on samples with different superlattice periods, enabling a determination of the time-dependent conductivity. We obtained sub-picosecond carrier capture times, indicating the potential of these devices as time domain THz detectors. We also performed optical-pump mid-IR probe experiments on dots-in-a-well (DWELL) detectors, which consist of InAs quantum dots sandwiched between thin In_0.15Ga_0.85As quantum wells (QW) that are subsequently placed in a GaAs matrix. By using a pump pulse to excite carriers in the bulk GaAs layers and tuning the mid-IR probe wavelength resonant with the transitions in the quantum wells and dots, we can track the relaxation of carriers from the bulk GaAs into the InGaAs quantum wells and finally into the InAs quantum dots. This enables us to track carrier relaxation from three to two to zero dimensions for the first time, to the best of our knowledge. In conclusion, our research into time-resolved mid-and-far-infrared dynamics in semiconductor nanostructures and correlated electron materials demonstrates the utility of ultrafast optical spectroscopy in studies of condensed matter systems, leading to advances in understanding their fundamental properties and optimizing them for different applications. Sponsor: Dr. Rittby Wednesday March 9 at 4:00 p.m. in SWR 357 Refreshments served between 3:00 and 4:00 p.m. during informal discussions with our visitor Dr. Xuan Gao Los Alamos National Laboratory The 2D metallic state and metal-insulator transition: two decades of controversy Abstract: The celebrated scaling theory of localization predicts that there is no true metallic ground state for disordered Fermi liquids in two dimensions (2D) in zero magnetic field. However, experiments in early 1990’s have revealed an intriguing metallic state and metal-insulator transition in various low density 2D systems. For these systems, carriers are strongly correlated, as characterized by the large value of r_s, the ratio between Coulomb interaction energy and the Fermi energy E_F. It is currently being debated that if the strong correlations can stabilize a metallic non-Fermi liquid phase in 2D. In this talk I will present transport experiments on dilute 2D holes with r_s >20 in some world highest quality Gallium Arsenide (GaAs) quantum wells down to temperatures as low as 0.01K. We find that a small parallel magnetic field (B_\|\|) suppresses the strength of the 2D metallicity without affecting its energy scale. In strong B_\|\| when the spins are all polarized, we observe a logarithmically diverging resistance of 2D holes at low T, as predicted by the scaling theory of localization, indicating the system is driven back to the Fermi liquid state. These experiments show that the 2D metallic behavior is closely related to the spins of the carriers. I will also discuss our recent observation of strongly enhanced hole-phonon coupling in dilute 2D GaAs hole system. References: X. P.A. Gao et al., Phys. Rev. Lett., 88, 166803 (2002); ibid 89, 016801 (2002); ibid 93, 256402 (2004); cond-mat/0501686, to appear in PRL (2005). Sponsor: Dr. Rittby Monday March 21 at 4:00 p.m. in SWR 357 Refreshments served between 3:15 and 4:00 p.m. during informal discussions with our visitor Dr. Yuri M. Strzhemechny Center for Materials Research The Ohio State University Studies of Nanoscale Distribution of Defects in Semiconductors Abstract: Defects in semiconductors are often detrimental for their optoelectronic and transport properties. Understanding and control of those defects usually requires nanoscale sensitivity. For that purpose we employ a combination of experimental surface sentitive techniques such as Low Temperature Photoluminescence Spectroscopy, Depth-Dependent Cathodoluminescence Spectroscopy, X-Ray Photoelectron Spectroscopy, Auger Electron Spectroscopy, Secondary Ion Mass Spectrometry, and Secondary Electron Microscopy. To illustrate the power of those techniques, we report some of our recent results for single-crystalline ZnO and polycrystalline Cu(In,Ga)Se₂ processed with remote inductively-coupled plasmas. Sponsor: Dr. Zerda Wednesday March 23 at 4:00 p.m. in SWR 357 Refreshments served between 3:15 and 4:00 p.m. during informal discussions with our visitor Dr. Ashutosh Tiwari NSF Center for Advanced Materials & Smart Structures Department of Materials Science & Engineering North Carolina State University Thin Films and Nanostructured Materials: Growth, Characterization and Multidisciplinary Applications Abstract: Nanoscience & Nanotechnology represents one of the hottest frontiers in Physical Sciences and Engineering. This is a multidisciplinary field and has tremendous applications in almost every field of Science & Technology. The word “Nanomaterials” is quite broad and involves a variety of structures ranging from zero dimensional atom clusters to three dimensional grain structures, from one dimensional superlattice structures to two-dimensional granular thin films. A common feature of all these systems is that they have at least one dimension in the nanometer range (1-100 nm). Confinement effects due to boundary conditions make “Nanostructured Materials” behave much differently than their bulk counterparts. In this talk, I will present some of my very exciting results related to these material systems. Major focus will be on following four topics: (i) Spintronics and Diluted Magnetic Semiconductors (ii) Nanodots for Magnetic Data Storage (iii) Ultra Sensitive Infrared Sensors (iv) Biocompatible Materials. Specifically, a new class of heteroepitaxial superlattice structure (La_0.7Sr_0.3MnO₃/ZnO) exhibiting giant magnetoresistance (GMR) at low magnetic fields (~100 Gauss) will be described. Experimental results about the growth and observation of room temperature ferromagnetism (RTF) in epitaxial thin films of transition metal (V, Mn, Co) doped ZnO and CeO₂ will be presented. These results will be compared with earlier theoretical predictions. This will be followed by our recent work on the synthesis of magnetic Nanodots for applications in ultrahigh density magnetic storage media. After this, fabrication of high quality NdNiO₃ based infrared sensors and their integration with Silicon substrate will be discussed. Finally, I will talk about some of our interesting results related to the synthesis of Silver doped Diamond like Carbon (DLC) films, which exhibit significant antimicrobial properties and act as excellent biocompatible materials. Sponsor: Dr. Zerda Tuesday March 29 at 4:00 p.m. in SWR 357 Refreshments served between 3:15 and 4:00 p.m. during informal discussions with our visitor Dr. Ruihua Cheng Materials Science Division and Center for Nanoscale Materials Argonne National Laboratory Properties of Magnetic Nanostructures Fabricated via Epitaxial Growth Abstract: Magnetic nanostructures are of great interests in recent years due to their technical applications as well as rich fundamental physics. While extensive progress has been made to understand magnetic films, our knowledge of one-dimensional (1D) and zero-dimensional (0D) ferromagnetism is limited. In this presentation, I will discuss the fabrication and characterization of low dimensional magnetic nanostructures, especially self-assembled magnetic nanodots on Ru(0001) substrates and nanowires on Pt(997) vicinal surface. Nanoscale phenomena such as dimensionality, domains and their interactions, and metastable states are explored by magnetic force microscopy (MFM), scanning tunneling microscopy (STM), magneto-optical Kerr effect (MOKE), spin polarized low energy electron microscopy (SPLEEM), and photoemission electron microscopy (PEEM). The shape, alignment and magnetic anisotropy of the self-assembled nanomagnets can be controlled by substrates modification. The potential application of nanostructures on nanoscale spin detection will be addressed as well. Sponsor: Dr. Zerda Thursday March 31 at 4:00 p.m. in SWR 357 Refreshments served between 3:15 and 4:00 p.m. during informal discussions with our visitor Dr. Anatoliy Glushchenko Liquid Crystal Institute Kent State University Controlling light by liquid crystals: recent frontiers Abstract: Liquid crystals are beautiful and still mysterious. I am fond of them for both reasons. My talk will introduce these fascinating materials and hopefully engage the audience to investigate further their intriguing science and applications. We have known of the existence of liquid crystals for more than 100 years. Research in the field is inherently multidisciplinary, engaging researchers in physics, chemistry, optics, mechanics, and mathematical simulations. Understanding the liquid crystal phase is an inherently certain three-dimensional problem requiring not only the visualization of complex molecular structures but also how these molecules organize in a myriad of complex geometries. Over the last few decades, scientists have effectively exploited the unique properties of liquid crystals to produce increasingly sophisticated displays. Combining liquid crystals with other materials has led to a great number of scientific discoveries and the formulation of even more fascinating materials. A great example is liquid crystal / polymer dispersions. Their study is breathtaking, and their application is very diverse, from nano-structured photonic devices, microscopic adaptive and diffractive optical elements, and large light modulators used for beam steering and missile defense systems. Sponsor: Dr. Zerda Friday April 8 at 1:00 p.m. in SWR 357 Pre-dissertation Michael Vick Department of Physics and Astronomy TCU Probing the Concordance Cosmology with Galaxy Cluster Substructure Refreshments and the Pre-dissertation Oral Examination will follow Sponsor: Dr. Quarles College of Science and Engineering Student Research Symposium Friday April 22 Wednesday April 27 at 3:30 p.m. in SWR 357 PHYS 50733 Colloquia These are 15 minute presentations of projects that students have worked on in Dr. Marcum's PHYS 50733 class. Billy Quarles - How comet morphology changes with solar system age Cort Spellman - Using cross-correlation techniques to measure gravitational redshifts of white dwarf stars Ryan Haygood - N-body simulations of interacting galaxies George Peyton - A JAVA program to predict the light curves of occulting binary star systems Department of Physics and Astronomy TCU Sponsor: Dr.Marcum Friday April 29 at 1:00 p.m. in SWR 357 Pre-dissertation Rafael Cardenas Department of Physics and Astronomy TCU Experimental Advances in the Production of Carbon Clusters Refreshments and the Pre-dissertation Oral Examination will follow Sponsor: Dr. Graham
	Copyright © 2002-06 Magnus Rittby / Kaoru Yoshida; Last Updated: Saturday, August 18, 2007