Anura Goonewardene

The time, size, viscosity, and temperature dependence of the Brownian motion of polystyrene microspheres

An upper division undergraduate laboratory module to study Brownian motion was developed using polystyrene microspheres suspended in a sample liquid cell that was isolated from its surroundings. The dependence of the Brownian motion of the microspheres on their radius, the time, the viscosity of the suspension liquid, and the temperature were measured using a CCD camera interfaced with a frame grabber and a computer. The motion of each particle was monitored for 5minutes and was found to be consistent with the Langevin formula for Brownian motion.

Two-dimensional nanotriangle and nanoring arrays on silicon wafer

Gold and tungsten were deposited on silicon wafer and/or glass substrates by using random incidence sputtering deposition and thermal vapor deposition techniques. Two-dimensional tungsten nanotriangle and gold nanoring arrays were obtained on the silicon wafer substrate and examined using scanning electron microscope and atomic force microscope analysis. The size of the equal tungsten nanotriangles is within 100 nm per side and 210 nm apart from each other. The size of gold nanorings is 220 nm diameter, 40 nm wide, 10 nm thick, and 560 nm apart from each other. No nanorings were found on the glass substrate. Mechanisms for the formation of nanoring arrays are discussed.

Imaging the Fermi surface of Cu using photoelectron spectroscopy

Abstract We have studied the Fermi surface of Cu using an ellipsoidal-mirror analyzer which gives two-dimensional images of photoelectron intensity versus emission angle. From these images, we have obtained the full Fermi surface of Cu in three-dimensional k -space. Our results are in excellent agreement with previous studies and provide new perspectives on Fermi surface studies.

Sustaining physics programs through interdisciplinary programs: A case study in nanotechnology

Many of the nation’s physics graduates come from bachelor’s granting institutions with small physics programs; of 505 bachelor’s granting programs, only 52 have 10 or more graduates each year. The current economic downturn is putting pressure on administrators to close low-enrolled programs. This emphasis on dollars and cents, combined with the high cost of equipping and maintaining laboratories and faculty lines, threatens the many small programs that collectively account for about 40% of all physics graduates each year. The Pennsylvania State System of Higher Education is not immune from these pressures. Programs that averaged less than 6 students per year for the past 5 years are deemed “low enrolled” and are subject to review. Of the 14 universities in our system, the smallest university already does not have a physics major. Of the 13 that do, 10 are low enrolled and one has been designated for closure in 2011 and tenured physics faculty given letters of retrenchment. The remaining programs are scrambling to develop strategies for survival, including collaboration with other schools and online delivery of low-enrolled upper division courses to reduce costs. If fewer than 6 graduates per year becomes the criterion for a low-enrolled program, 73% of the 505 bachelor’s-only degree granting institutions in the U.S. is “under enrolled.” Some, if not many, of these programs might be eliminated or significantly scaled back to the status of a “service” discipline unless they take active steps to increase enrollment. In these times the benefits to students of a thriving physics program are often secondary to the bottom line. We describe here the steps we took to grow our B.S. Physics program from an average of 1.5 graduates per year ten year average to an average of 7.2 graduates per year five year average by integrating nanotechnology into the curriculum. Our department now produces the third highest number of physics graduates in our 14 university system despite the fact that we are the third smallest in total undergraduate enrollment 5450 students . Applied physics and minor in nanotechnology. In 2003, we recognized the need to attract nontraditional students to the physics program by developing an applied physics track that incorporates nanotechnology into the physics curriculum. By 2008, we saw that a significant number of biology and chemistry majors were becoming interested in nanotechnology and applying it within their disciplines. The recognition that the tools and techniques of nanotechnology have applications across disciplines presaged the growing trend toward “convergence science,” prompting us to develop a minor in nanotechnology for biology and chemistry majors. The minor piggybacks on the curriculum we developed and imple-

Preparation of Green, Yellow and Red Long Persistent Nanophosphors

Long persistent nanophosphors of ZnS:Cu (Green), ZnO:Mn (Yellow) and CaO:Eu (Red) were prepared through precipitation method. n-heptane was used as a stabilizer to control the particle growth. Green emission of Cu in ZnS was found at 506 nm, yellow emission of Mn in ZnO was found at 572 nm, and red emission of Eu in CaO is found at 616 nm. The average growth rate of CaO nanophosphor was 4.72 nm/s. Adding a stabilizer can stop the particle growth and aggregation. Smaller particle size was obtained by adding n-Heptanes at earlier time.

Sulfide Phosphors for LED White Light Sources

Several sulfide phosphors, such as CaS:Ce3+,Na+, CaS:Eu2+,Ce3+, ZnS:Te,Mn, ZnS:Se,Te,Mn and ZnS:Ce,Li were prepared and their excitation and luminescent spectra were investigated. The possible applications in LED-Phosphors white light devices are discussed.

Preliminary performance and experiments from the high resolution plane grating monochromator at the center for advanced microstructures and devices

Abstract A soft X-ray plane grating monochromator installed at Louisiana State Universitys Center for Advanced Microstructures and Devices has been characterized and the first experimental results obtained. The monochromator is a modified SX-700 design which uses a moveable pre-mirror to allow the instrument to remain in focus over an energy range of 8 to 1200 eV. Since the pre-mirror motion is independent of the grating rotation, the monochromator can be used in three different modes: maximum resolution (fixed focus), maximum throughput, and maximum higher-order rejection. Absolute intensity measurements for all orders are reported for two fixed angles of the pre-mirror and for the fixed-focus mode. Results from the first experiments using the monochromator are reported.