Efficient Photon Capturing with Ordered Three-Dimensional Nanowell Arrays

Leung, Siu Fai; Yu, Miao; Lin, Qingfeng; Kwon, Kyungmook; Ching, Kwong-Lung; Gu, Leilei; Yu, Kyoungsik; Fan, Zhiyong

doi:10.1021/nl3014567

Cited by 131 publications

(154 citation statements)

References 34 publications

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“…These organic solvent solutions including the electrolyte allow ultra-high voltage anodizing without burning, different from aqueous solutions. Fabrication of ordered porous alumina with higher than 500 nm and micrometer-scale cell diameters is successfully achieved via anodizing in organic solvents, including citric acid electrolyte [113][114][115][116]. Figure 8a shows the schematic models of the vertical cross-section of the anodic porous oxide films formed by self-ordering anodizing.…”

Section: Fabrication Of Highly Ordered Porous Aluminum Oxidementioning

confidence: 99%

Porous Aluminum Oxide Formed by Anodizing in Various Electrolyte Species

Kikuchi¹,

Nakajima²,

Nishinaga³

et al. 2015

CNANO

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Anodizing of aluminum and its alloys is widely investigated and used for corrosion protection, electronic devices, and micro-/nanostructure fabrication. Anodizing of aluminum in acidic solutions causes formation of porous aluminum oxide films, which consists of numerous hexagonal cells perpendicular to the aluminum substrate, and each cell has nanoscale pores at its center. Recently, highly ordered porous aluminum oxide has been widely investigated for various novel nanoapplications. In this review article, we introduce the fundamentals of anodic oxide films including barrier and porous oxides. Then, we summarize the electrolyte species used so far for porous oxide fabrication and describe the self-ordering conditions during anodizing in these electrolyte solutions. Fabrication of highly ordered porous oxides through the vertical section can be achieved by a two-step anodizing and nanoimprint technique. Various nanoapplications based on the ordered porous oxide are also introduced.

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Section: Fabrication Of Highly Ordered Porous Aluminum Oxidementioning

confidence: 99%

Porous Aluminum Oxide Formed by Anodizing in Various Electrolyte Species

Kikuchi¹,

Nakajima²,

Nishinaga³

et al. 2015

CNANO

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“…Citric acid anodizing operates over an anodizing voltage range of approximately 260-540 V. However, non-uniform black oxides are easily formed by a phenomenon called "burning" during citric acid anodizing because of localized breakdown under high electric fields, and it is difficult to obtain high-aspect-ratio ordered porous alumina. Therefore, ethylene glycol mixture solutions containing citric acid and other electrolytes have been developed for steady-state oxide growth to avoid burning during anodizing [43,44]. Anodic porous alumina, which possesses a large-scale cell size greater than 500 nm, can be successfully formed by anodizing in these mixture solutions.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of Self-Ordered Porous Alumina via Etidronic Acid Anodizing and Structural Color Generation from Submicrometer-Scale Dimple Array

Kikuchi

Nishinaga

Natsui

et al. 2015

Electrochimica Acta

107

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Highly ordered anodic porous alumina with a large-scale cell diameter was successfully fabricated via anodizing in a new electrolyte, etidronic acid (1-hydroxyethane-1,1-diphosphonic acid). High-purity aluminum specimens were anodized in a 0.3 M etidronic acid solution under constant current density and voltage conditions. Etidronic acid anodizing at 210 to 270 V at the appropriate temperature caused the anodic porous alumina to exhibit self-ordering behavior, and periodic nanostructures measuring 530 to 670 nm in cell diameter were fabricated on the aluminum substrate. The self-ordering voltage and the corresponding cell diameter could be increased without burning by systematically increasing the stepwise voltage. Two-step etidronic acid anodizing without nanoimprinting can easily yield the formation of highly ordered anodic porous alumina with a large-scale cell diameter. A submicrometer-scale dimple array fabricated via etidronic acid anodizing and subsequent selective oxide dissolution gave rise to bright structural color with a rainbow distribution.Keywords: Anodizing; Etidronic Acid; Anodic Porous Alumina; Self-Ordering; Structural Color 3 IntroductionAnodizing aluminum and its alloys in acidic electrolyte solutions results in the formation of porous anodic oxide films (anodic porous alumina) with numerous nanometer-scale pores [1][2][3]. Most importantly, anodic porous alumina is self-ordered when anodized under the appropriate electrochemical conditions in a given acidic solution, and consequently, high-aspect-ratio anodic porous alumina with an ideal cell arrangement can be easily obtained [4][5][6][7][8][9]. In the self-ordering anodizing, it is well known that the cell diameter of the anodic porous alumina, D, is strongly related to the self-ordering voltage, U s : a) D = 50-60 nm at U s = 19-25 V for sulfuric acid [10,11], b) 100 nm at 40 V for oxalic acid [4,11,12] [35][36], and magnetic nanomaterials [37].Because the cell diameter of self-ordered porous alumina fabricated by typical anodizing in aqueous solutions is limited to approximately 500 nm at 200 V [5,18], larger cell diameters that correspond to visible-light wavelengths ranging between 500 nm and 800 nm are required to expand the applicability of porous alumina in the field of optics. Malic acid anodizing provides a relatively high anodizing voltage and, consequently, a larger cell diameter, D = 300-800 nm at 200-350 V [38,39]. However, to date, ordered anodic porous alumina has not been obtained by malic acid anodizing. As an alternative electrolyte for high-voltage anodizing, citric acid has also been investigated by several research groups [39][40][41][42]. Citric acid anodizing operates over an anodizing voltage range of approximately 260-540 V. However, non-uniform black oxides are easily formed by a phenomenon called "burning" during citric acid anodizing because of localized breakdown under high electric fields, and it is difficult to obtain high-aspect-ratio ordered porous alumina. Therefore, ethylene glycol mixture soluti...

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“…The conventional surface texturing with alkaline or acidic solution for sub-10-mmthick Si substrates requires additional masking steps including photolithography 15 , and it is hard to implement on thin substrates with high yield 16 . In the past several years, significant effort has been focused on enhancing the light absorption by nanoscale light trapping using nanowires 8,[17][18][19] , nanocones [20][21][22] , nanodomes 7 and nanoholes [23][24][25][26] . Despite the exciting success in light trapping, the power conversion efficiencies of nanostructured Si solar cells, however, remain below 19% for thick devices 26 and below 11% for thin devices 27 .…”

mentioning

confidence: 99%