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2012 Transfer-to-Excellence Research Experiences for Undergraduates Program (TTE REU) Characterization of layered gallium telluride (GaTe) Omotayo O Olukoya.

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Presentation on theme: "2012 Transfer-to-Excellence Research Experiences for Undergraduates Program (TTE REU) Characterization of layered gallium telluride (GaTe) Omotayo O Olukoya."— Presentation transcript:

1 2012 Transfer-to-Excellence Research Experiences for Undergraduates Program (TTE REU) Characterization of layered gallium telluride (GaTe) Omotayo O Olukoya (Chabot College) PI : Oscar Dubon Mentor : Jose Fonseca Vega Lawrence Berkeley National lab 1

2 2012 Transfer-to-Excellence Research Experiences for Undergraduates Program (TTE REU) Layered semiconductors Complex structure Manipulate band-gap. 2 GaTe (1.045 nm) Recent discovery nm adapted from D. V. Rybkovskiy et al., PRB (2011) Mak, K.F., et al., Phys Rev Lett. 105, (2010). GaSe MoS 2 Chalcogenide

3 2012 Transfer-to-Excellence Research Experiences for Undergraduates Program (TTE REU) GaTe a.Monoclinic crystalline structure in bulk. parameter constant: a = Å, b = Å, c = Å, ϒ = o 3 b. Goes from monoclinic to hexagonal in thin films d. P - type What to look for? c. Direct band gap of 1.69 eV at room temperature. What do we know?

4 2012 Transfer-to-Excellence Research Experiences for Undergraduates Program (TTE REU) Method nm of thermally oxidized SiO 2 on Si was used. Ultra sonication  Isopropyl alcohol  Acetone Oxygen plasma Standard RCA cleansing method  Substrate treatment

5 2012 Transfer-to-Excellence Research Experiences for Undergraduates Program (TTE REU) Method cont.  Scotch tape method was develop by Andre Geim 5  Optical microscopy  Mechanical exfoliation  Transfer

6 2012 Transfer-to-Excellence Research Experiences for Undergraduates Program (TTE REU) Method cont. 6  Atomic Force microscopy (AFM) Tapping mode AFM images 8 nm

7 2012 Transfer-to-Excellence Research Experiences for Undergraduates Program (TTE REU) Method cont. 7  Raman spectroscopy o A 15mW Ar ion laser (514.5 nm) was used.  Photoluminescence spectroscopy (PL) o A 488 nm blue laser

8 2012 Transfer-to-Excellence Research Experiences for Undergraduates Program (TTE REU) Raman result Raman spectra cont. a. New peaks between 140 & 280 of Raman shift 8

9 2012 Transfer-to-Excellence Research Experiences for Undergraduates Program (TTE REU) Raman’s result cont. Raman spectra b. Horizontal shift

10 2012 Transfer-to-Excellence Research Experiences for Undergraduates Program (TTE REU) PL result 10 Correlation between laser intensity and counts

11 2012 Transfer-to-Excellence Research Experiences for Undergraduates Program (TTE REU) PL result cont. Correlation between thickness and count 11

12 2012 Transfer-to-Excellence Research Experiences for Undergraduates Program (TTE REU) Conclusion  GaTe exhibits some anisotropic features.  It will take further research to know what properties are actually isolated from bulk.  Great chances of being able to cleave down to a monolayer on SiO 2 substrate. 12

13 2012 Transfer-to-Excellence Research Experiences for Undergraduates Program (TTE REU) Next step Cleave down to a monolayer Take more Raman Take low temperature PL Devices and application? 13

14 2012 Transfer-to-Excellence Research Experiences for Undergraduates Program (TTE REU) Acknowledgment Prof Oscar Dubon (PI) Jose Fonseca Vega (mentor) Dubon’s Group –Alex Luce (PL) –Erick Ulin-Avila Dr. Sharnia Artis Shuk H Chan Center for Energy Efficient Electronics (E3S) National Science Foundation (NSF) Q & A ? 14


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