1. Abstract
The experiment results associated with the reflectance of randomly distributed
Platinum Bulk Metallic Glass (Pt-BMG) nanopillars (diameter = 100 nm) are
presented. Pillars with respective heights equaling 500 nm, 700 nm, 1500 nm
and 2000 nm were studied. Linearly polarized laser light with wavelengths 457
nm, 532 nm, and 671 nm (Power 250 mW- 300 mW), respectively, were
employed. A commercially available reference sample with known reflectance
was used. The diffused reflection form each sample was measured by means
of an integrating sphere. While the reflectance decreases with increasing pillar
height , it increases as a function of laser light wavelength.
Background
Conclusion
Physical characteristics of Platinum Bulk Metallic Glass:
a. Extreme strength at low temperature .
b. High flexibility at high temperature.
c. Resistant to Wear.
Methodology
Properties
Experiment Results
SEM Images of Pt-BMG nano pillars, diameter =100 nm
The reflectance of Pt-BMG nano-pillars were characterized. Pt-BMG produces diffuse reflection
when a linearly polarized laser light impinges upon it. Reflectance of Pt-BMG nano-pillars
increases as the pillar height decrease at a fixed wavelength. Reflectance increase when λ
increase at a fixed height h.
Materials and Equipment
Equipment
• Integrating Sphere.
• Photo detectors.
• Keithly 2400 Multi-meter.
• Agilent 34401 Multi-meter.
• Stepper motor.
• Newport ESP 300 Stepper Motor Controller.
• PC with Labview program package.
Acknowledgements
Special thanks go to: a.) Dr. Ayrton A. Bernussi of the ECE Department/NTC, TTU for facilitating
and hosting the research in his laboratory and mentoring b.) Hendra J. Tarigan of ECE
Department /NTC, TTU for mentoring and c.) Dr. Golden Kumar and Lianci Liu (Mechanical
Engineering Department, TTU) for fabricating the Pt BMG nanorods and collaboration and d.) Dr
Vladimir Kuryatkov of NTC, TTU for acquiring the SEM images. (Without these people the
research would not have taken place).
Bibliography
1.Chen, Mingwei. "A brief overview of bulk metallic glasses." NPG Asia Materials3.9 (2011):
82-90.
2. G. Kumar, A. Desai, J. Schroers, Bulk metallic glass: the smaller the better, Advanced
Materials, 23 (2011) 461.
3. Yang, Z. P., Ci, L., Bur, J. A., Lin, S. Y., & Ajayan, P. M. (2008). Experimental observation of
an extremely dark material made by a low-density nanotube array. Nano letters, 8(2), 446-
451.
Purpose
Study of the diffuse reflectance associated with randomly distributed Pt-BMG
nano pillars. In particular, the influence of pillar height and wavelength
variations, respectively, on reflectance is investigated.
Diffusedly reflected rays of light from sample undergo multiple reflection inside the
sphere and light intensity probed by a silicon photo detector (I = f(ϴi).
To prevent leakage of stray light the setup is covered by flexible dark plastic.
Background light and laser light temporal fluctuations and drifts are also monitored
ensuring high S/N. Real time light intensity and angular displacement are acquired
by use of LabView.
Experiment Technique
When a laser light impinges upon the nano pillars at a certain angle of
incidence, diffuse reflection is generated. Integrating sphere is employed to
collect such diffusedly reflected light . Rotating sample holder is placed at the
center of the sphere. Stepper motor rotates the sample holder at desired angular
displacements with respect to the incident laser light. A photo detector is placed
at a fixed port on the sphere to probe the reflected light.
Experiment Results (continued)
Future Work
Nelson Spulveda Ramos1, Hendra J. Tarigan2, Ayrton. A. Bernussi3, Lianci Liu4, Golden Kumar5
1. Department of Electrical and Computer Engineering, University of Puerto Rico, Mayagüez, PO Box 9000, Mayagüez, PR 00681-9000, USA.
2,3. Department of Electrical and Computer Engineering, Edward Whitacre Jr. College of Engineering, Texas Tech University, Box 43102, Lubbock, TX 79409, USA.
4,5. Department of Mechanical Engineering, Edward Whitacre Jr. College of Engineering, Texas Tech University, Box 41021, Lubbock, TX 79409, USA.
Determining the complex values value of n =n+ ik and ε = ε’+i ε” and absorption associated
with the Pt-BMG nano pillars.
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Reflectivity
Angle of Incidence [Degrees]
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0.2
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Reflectivity
Angle of Incidence [Degrees]
Reflectance as a function of pillar heights: as height increases, reflectance decreases
Materials
Pt-BMG, reference sample, linearly polarized lasers (λ= 457 nm, λ= 532 nm
and λ= 671 nm, Power= 250 mW-300 mW), Linear polarizer, Half-wave plate,
beam splitter, neutral density filters, micro translation stage, posts, black
flexible plastic cover, and iris.
Dr. Bernussi’s Research group, Nano Tech Center, Texas Tech University
Reflectance as a function of laser light
wavelengths. As the wavelength increases
the reflectance also increases.
Reflectance as a function of pillar height
when green laser light λ=532 nm is used .
Top view image of randomly distributed nano pillars (left) and the
Image of same nano pillar taken at a wider view angle (right).
λ=671 nm
λ=532 nm λ=671 nm
λ=532 nm
Dr. Bernussi’s Research Group, Nano Tech Center, Texas Tech University
Diffuse Reflection from Platinum Bulk Metallic Glass (Pt-BMG) nano pillars
700nm
2000nm 1500nm
500nm
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Reflectivity
Angle of Incidence [Degrees]
700nm
2000nm 1500nm
500nm
Top View of Experimental Setup
Laser Light
Sample Holder
Stepper Motor
Laser Light Source
PD
PD
Beam splitter
Linear polarizer
Sphere
NDF
NDF
Cardboard
PD= Photodector
NDF= Neutral Density Filter
Half wave plate
Iris