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Bio-inspired, subwavelength surface ...

Lora Gonzalez, Federico.

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Bio-inspired, subwavelength surface structures to control reflectivity, transmission, and scattering in the infrared.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Bio-inspired, subwavelength surface structures to control reflectivity, transmission, and scattering in the infrared./
Author:	Lora Gonzalez, Federico.
Description:	161 p.
Notes:	Source: Dissertation Abstracts International, Volume: 76-09(E), Section: B.
Contained By:	Dissertation Abstracts International76-09B(E).
Subject:	Nanoscience. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3689951
ISBN:	9781321696455

Bio-inspired, subwavelength surface structures to control reflectivity, transmission, and scattering in the infrared.
Lora Gonzalez, Federico.

Bio-inspired, subwavelength surface structures to control reflectivity, transmission, and scattering in the infrared. - 161 p.

Source: Dissertation Abstracts International, Volume: 76-09(E), Section: B.

Thesis (Ph.D.)--University of California, Santa Barbara, 2015.

This item must not be sold to any third party vendors.

Controlling the reflection of visible and infrared (IR) light at interfaces is extremely important to increase the power efficiency and performance of optics, electro-optical and (thermo)photovoltaic systems. The eye of the moth has evolved subwavelength protuberances that increase light transmission into the eye tissue and prevent reflection. The subwavelength protuberances effectively grade the refractive index from that of air (n=1) to that of the tissue (n=1.4), making the interface gradual, suppressing reflection. In theory, the moth-eye (ME) structures can be implemented with any material platform to achieve an antireflectance effect by scaling the pitch and size of protuberances for the wavelength range of interest.

ISBN: 9781321696455Subjects--Topical Terms:

587832
Nanoscience.

Bio-inspired, subwavelength surface structures to control reflectivity, transmission, and scattering in the infrared.
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020 $a 9781321696455
035 $a (MiAaPQ)AAI3689951
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040 $a MiAaPQ $c MiAaPQ
100 1 $a Lora Gonzalez, Federico. $3 3171493
245 1 0 $a Bio-inspired, subwavelength surface structures to control reflectivity, transmission, and scattering in the infrared.
300 $a 161 p.
500 $a Source: Dissertation Abstracts International, Volume: 76-09(E), Section: B.
500 $a Adviser: Michael J. Gordon.
502 $a Thesis (Ph.D.)--University of California, Santa Barbara, 2015.
506 $a This item must not be sold to any third party vendors.
520 $a Controlling the reflection of visible and infrared (IR) light at interfaces is extremely important to increase the power efficiency and performance of optics, electro-optical and (thermo)photovoltaic systems. The eye of the moth has evolved subwavelength protuberances that increase light transmission into the eye tissue and prevent reflection. The subwavelength protuberances effectively grade the refractive index from that of air (n=1) to that of the tissue (n=1.4), making the interface gradual, suppressing reflection. In theory, the moth-eye (ME) structures can be implemented with any material platform to achieve an antireflectance effect by scaling the pitch and size of protuberances for the wavelength range of interest.
520 $a In this work, a bio-inspired, scalable and substrate-independent surface modification protocol was developed to realize broadband antireflective structures based on the moth-eye principle. Quasi-ordered ME arrays were fabricated in IR relevant materials using a colloidal lithography method to achieve highly efficient, omni-directional transmission of mid and far infrared (IR) radiation.
520 $a The effect of structure height and aspect ratio on transmittance and scattering is explored, with discussion on experimental techniques and effective medium theory (EMT). The highest aspect ratio structures (AR = 9.4) achieved peak single-side transmittance of 98%, with >85% transmission for lambda = 7--30 microns. A detailed photon balance constructed by transmission, forward scattering, specular reflection and diffuse reflection measurements to quantify optical losses due to near-field effects will be discussed. In addition, angle-dependent transmission measurements showed that moth-eye structures provide superior antireflective properties compared to unstructured interfaces over a wide angular range (0--60° incidence).
520 $a Finally, subwavelength ME structures are incorporated on a Si substrate to enhance the absorption of near infrared (NIR) light in PtSi films to increase Schottky-barrier detector efficiency. Absorbance enhancement of 70--200% in the lambda =1--2.5 micron range is demonstrated in crystalline PtSi films grown via electron beam evaporation of Pt and subsequent vacuum annealing. Low total reflectance (<10%) was measured in ME films, demonstrating the efficacy of the moth eye effect. Effective medium theory and transfer matrix calculations show that the large absorption enhancement at short wavelengths is partly due to light trapping, which increases the effective optical path length in PtSi. The demonstrated structures are promising candidates for efficient PtSi/p-Si Schottky barrier diode detectors in the NIR. Results further suggest a general method for relatively low-cost absorption enhancement of backside-illuminated detectors based on a wide variety of infrared absorptive materials.
520 $a The methods presented here to fabricate quasi-ordered ME structures provide a general platform for creating antireflective structures in many different materials, devices, and bandwidths. Furthermore, understanding the relationship between protuberance shape, height, aspect ratio, etc. and performance (antireflection, scattering loss, etc.) can guide the design of antireflective surfaces for different applications (for example, in certain applications, large amounts of forward scattering is desired, e.g. photovoltaics).
590 $a School code: 0035.
650 4 $a Nanoscience. $3 587832
650 4 $a Engineering, Materials Science. $3 1017759
650 4 $a Engineering, Chemical. $3 1018531
690 $a 0565
690 $a 0794
690 $a 0542
710 2 $a University of California, Santa Barbara. $b Chemical Engineering. $3 1028918
773 0 $t Dissertation Abstracts International $g 76-09B(E).
790 $a 0035
791 $a Ph.D.
792 $a 2015
793 $a English
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3689951