Comparing Metal Nanoparticle Growth on Si vs ITO

Aaron Allen

University of Rochester
Center for Entrepreneurship

OPT407: Practical Electron Microscopy
Spring 2015

Final Project


Introduction

  1. Light Trapping
  2. Proposed Project
Characterization Techniques
  1. Sample Preparation
  2. Atomic Force Microscopy
  3. Secondary Electron Microscopy
  4. Backscattered Electron Detection
  5. Differential Interference Contrast
  6. Electron Flight Simulation

Conclusions and Acknowledgements

  1. Conclusion
  2. Acknowledgements
  3. Future Work
  4. References
  5. Comments


 

Introduction

 1. Light Trapping

Photovoltaic cells (PCs) are potentially a revolutionary technology for energy applications.  Currently, PCs are limited by low efficiency and expensive cost.  Proposed methods to improve solar cell efficiency are usually via improving light absorption, or avoiding loss of electricity/heat after absorption.  The preferred method of improving light absorption is to introduce nanoparticles that create a light-trapping effect on incident light.  The secondary benefit is that light trapping allows the thickness (and hence cost) of solar cells to decrease.

The effectiveness of light trapping particles is dependent upon the substrate material, the as well as the material, pitch distance, shape, and dimensions of the nanoparticles.  The mechanism of light trapping is also affected by the placement depth of nanoparticles.  Particles placed on the top of a structure exhibits light trapping by scattering and angular redistribution of incoming light.  Embedded particles exhibit near-field enhancements of incident light through the creation of localized surface plasmons.[1]


 

2. Proposed Project

In this project, I propose to compare the growth of silver nanoparticles and gold nanoparticles on ITO vs Silicon substrates.  The purpose of the project is to test the uniformity of growing techniques so as to facilitate engineering of the dispersion properties of the cell through nanoparticle arrays. Additionally, at different sputtering rates, I expect to see a transition between nanoislands of metal into a more uniform distribution. Explorable deliverables are: uniformity of array distances; consistent hemispherical shapes for most (if not all) nanoparticles; and consistent heights. These deliverables are analyzed via atomic force microscopy, secondary electron microscopy, backscattered electron detection, differential interference contrast, and electron flight simulation.




 

Characterization Techniques

 

1. Sample Preparation

The as prepared samples were sputter coated with gold and silver. I used three sputtering times for each metal: 10 seconds, 20 seconds, and 30 seconds. These sputtering times are designated thin, medium, and thick, respectively. This corresponds to sputtered heights of 1 nm, 2 nm, and 3 nm respectively.

 

2. Atomic Force Microscopy

 

Figure 1:

 

3. Secondary Electron Microscopy

    

Figure 2:

 

4. Backscattered Electron Detection

    

Figure 3:

 

5. Differential Interference Contrast

     

Figure 4:

 

6. Electron Flight SImulation

  

Figure 5:

 

 

  

 

 

   



 

CONCLUSION AND ACKNOWLEDGEMENTS

 

1. Conclusion

 

 

2. Acknowledgements

Special thanks to Brian McIntyre, course instructor, for his help in designing the project and for being an important resource for knowledge and experimental technique.

 

3. References

1. Studies of metallic nanostructures and their application in photovoltaics

Light: Science & Applications (2014) 3, e161; doi:10.1038/lsa.2014.42
Published online 25 April 2014


 

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