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Ranu Nayak   Dr.  University Lecturer 
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Ranu Nayak published an article in January 2019.
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Top co-authors
Harsimran Singh Bindra

5 shared publications

Nanotechnology, Amity Institute of Nano Technology, Noida, Uttar Pradesh, INDIA

Tushar Kumeria

5 shared publications

University of Queensland School of Pharmacy, Brisbane, Queensland, AUSTRALIA

Publication Record
Distribution of Articles published per year 
(2016 - 2019)
Total number of journals
published in
Article 0 Reads 0 Citations An improved strategy for transferring and adhering thin nanoporous alumina membranes onto conducting transparent electro... Harsimran Singh Bindra, A B V Kiran Kumar, Somnath Chanda Ro... Published: 03 January 2019
Nanotechnology, doi: 10.1088/1361-6528/aae6e4
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This article presents a new method for transferring and enhancing the adhesion of thin nanoporous alumina (NPA) membranes onto non-atomically flat substrates like Fluorine doped Tin Oxide (FTO) coated glass. The study reports use of Glycerol as an additive to reduce the brittleness of the Polystyrene filler that was used to fill the pores of the NPA membrane. Besides, a new refluxing based method is reported here for complete removal of the Polystryrene filler from the porous channels of Alumina. The adhesion between NPA membrane and an underlying electrode was enhanced by electrodepositing a thin (~ 40 nm) intermediate layer of conducting polymer Polyaniline (PANI). The PANI layer acts as an efficient electrostatic adhesive between the NPA and the conducting glass electrode and ensured ultra-strong adhesion of NPA membrane that survived the harsh conditions of CdTe nanowire electrodeposition (60 °C temperature and acidic electrolyte) without delamination for 30 min. The resulting nanowires clearly templated the structure of NPA and displayed free-standing nanowires over a large area with diameter of around 60 nm and length approximately 2.8 µm (aspect ratio ~ 47) and an areal density of 5.9 × 1012 nanowires/cm2. Total optical absorption measurement on the free-standing CdTe nanowires exhibited an enhancement by 45% over a wavelength range of 350 nm to 1400 nm as compared to CdTe planar thin film of same thickness.
Article 0 Reads 0 Citations Rapid Processing of Wafer-Scale Anti-Reflecting 3D Hierarchical Structures on Silicon and Its Templation Harsimran Singh Bindra, JaiKrishna R., Tushar Kumeria, Ranu ... Published: 18 December 2018
Materials, doi: 10.3390/ma11122586
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Hierarchically structured silicon (Si) surfaces with a combination of micro/nano-structures are highly explored for their unique surface and optical properties. In this context, we propose a rapid and facile electroless method to realize hierarchical structures on an entire Si wafer of 3″ diameter. The overall process takes only 65 s to complete, unlike any conventional wet chemical approach that often combines a wet anisotropic etching of (100) Si followed by a metal nanoparticle catalyst etching. Hierarchical surface texturing on Si demonstrates a broadband highly reduced reflectance with average R% ~ 2.7% within 300–1400 nm wavelength. The as-fabricated hierarchical structured Si was also templated on a thin transparent layer of Polydimethylsiloxane (PDMS) that further demonstrated prospects for improved solar encapsulation with high optical clarity and low reflectance (90% and 2.8%).
CONFERENCE-ARTICLE 36 Reads 0 Citations <strong>Rapid and Facile Fabrication of Wafer Scale Silicon Hierarchical Structures with Broadband Ultra High Anti-Refle... Harsimran Bindra, Jai Krishna --, Tushar Kumeria, Ranu Nayak Published: 15 May 2018
Proceedings of The 3rd International Electronic Conference on Materials Sciences, doi: 10.3390/ecms2018-05223
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Nanostructuring of Silicon surface has perceived exponential growth over time due to its high demanding properties like superhydrophobicity and high anti-reflection [1]–[3]. Especially hierarchical structures (combination of micro- and nano- structures) on Silicon with significantly increased surface area has demonstrated enhanced optical and surface wettability properties, making it highly suitable for applications like self-cleaning, solar cell, photoluminescence, contamination prevention, etc [3]–[5]. Various techniques like vapour-liquid-solid (VLS), reactive ion etching (RIE), electrochemical etching and wet anisotropic electroless etching have been optimised for  micro- and nanostructuring over Silicon surface [5]–[9]. Methods like VLS and RIE are expensive and complicated. Wet electrochemical and electroless etching processes are simpler but electrochemical etching gives a very non-uniform porous structure and electroless etching only gives rise to microstructure and is also dependent on the orientation of Silicon surface. Nanostructuring of Silicon wafers using metal assisted etching has also been reported which is a rapid process [4], [10]. However, this process only results in the formation of nanostructured Silicon. There are reports where wet chemical etching and metal assisted etching process have been combined to realize hierarchical structures on Silicon but it does require longer time and large area uniformity in the formation of hierarchical structures is unpredictable [3], [11]. 

In this work, for the first time we propose an extremely fast and facile electroless method of fabricating hierarchical structures on Silicon wafer covering a large area. Added major benefits to this proposed method is that complete wafer can be textured within 3 to 8 minutes time span and is not dependent on the orientation or doping concentration of Silicon.

The unpolished side of a commercial Silicon wafer having grooved cup shaped microstructures on it was used as the base to deposit silver (Ag) nanoparticles electrolessly. After the Ag nanoparticle deposition for varied time between 30 s to 2 min, the Silicon wafer was etched for different time duration (1 min to 7 min) in dilute mixture of Hydrofluoric acid (HF) and Hydrogen peroxide (H2O2). Eventually the Ag nanoparticles were etched away in dilute Nitric acid leaving behind the hierarchical structures of Silicon unaffected. Pyramidal shaped microstructured Si surface was also used for deposition of Ag nanoparticles followed by a similar processing as mentioned above.

Diffused optical reflectance measurement on the hierarchical structured Silicon showed significant reduction by 46% in comparison to plane polished Silicon. Moreover insignificant variation in reflectance was observed over a broad wavelength range of 300 nm to 1400 nm.

It is concluded that such facile large area processing of hierarchical anti-reflecting structures on Si can be extremely beneficial for optical applications using Silicon.


[1]      Y. Cao et al., “Fabrication of silicon wafer with ultra low reflectance by chemical etching method,” Appl. Surf. Sci., vol. 257, no. 17, pp. 7411–7414, 2011.

[2]      Y. Xiu, L. Zhu, D. W. Hess, and C. P. Wong, “Hierarchical silicon etched structures for controlled hydrophobicity/ superhydrophobicity,” Nano Lett., vol. 7, no. 11, pp. 3388–3393, 2007.

[3]      D. Qi et al., “Simple Approach to Wafer-scale Self-cleaning Antireflective Surfaces,” pp. 1–5.

[4]      W.-F. Kuan and L.-J. Chen, “The preparation of superhydrophobic surfaces of hierarchical silicon nanowire structures.,” Nanotechnology, vol. 20, no. 3, p. 35605, 2009.

[5]      Y. Xiu, S. Zhang, V. Yelundur, A. Rohatgi, D. W. Hess, and C. P. Wong, “Superhydrophobic and Low Light Reflectivity Silicon Surfaces Fabricated by Hierarchical Etching,” Langmuir, vol. 24, no. 18, pp. 10421–10426, Sep. 2008.

[6]      C. R. Tellier and A. Brahim-Bounab, “Anisotropic etching of silicon crystals in KOH solution,” J. Mater. Sci., vol. 29, no. 22, pp. 5953–5971, 1994.

[7]      G. Barillaro, A. Nannini, and M. Piotto, “Electrochemical etching in HF solution for silicon micromachining,” Sensors Actuators A Phys., vol. 102, no. 1–2, pp. 195–201, Dec. 2002.

[8]      V. Schmidt, S. Senz, and U. G?sele, “Diameter-Dependent Growth Direction of Epitaxial Silicon Nanowires,” Nano Lett., vol. 5, no. 5, pp. 931–935, May 2005.

[9]      F. Marty et al., “Advanced etching of silicon based on deep reactive ion etching for silicon high aspect ratio microstructures and three-dimensional micro- and nanostructures,” Microelectronics J., vol. 36, no. 7, pp. 673–677, Jul. 2005.

[10]     S. Gielis, M. H. vander Veen, S. De Gendt, and P. M. Vereecken, “Silver-assisted Etching of Silicon Nanowires S. Gielis,” ECS Trans., vol. 33, no. 18, pp. 49–58, 2011.

[11]     D. Z. Dimitrov and C.-H. Du, “Crystalline silicon solar cells with micro/nano texture,” Appl. Surf. Sci., vol. 266, pp. 1–4, 2013.

Article 0 Reads 0 Citations Controlled and Selective Growth of 1D and 3D CdTe Nanostructures through a Structurally Engineered Porous Alumina Templa... Harsimran Singh Bindra, Subish John, Somnath C. Roy, Om Prak... Published: 15 December 2017
Journal of The Electrochemical Society, doi: 10.1149/2.0091804jes
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Current manuscript describes porous alumina (PA) template assisted electrodeposition of high aspect ratio nanowires and dense hierarchical structures of CdTe. We demonstrate here for the first time that simple structural engineering of a PA template can lead to electrochemical growth of diverse shapes of CdTe nanostructures. Facile and cost-effective modifications have been implemented for the fabrication of self-organized through-hole PA membrane and its transfer onto any rough substrate. These modifications have facilitated extended duration (30 minute to 1 hour) electrodeposition of CdTe nanostructures at high bath temperature of 60°C without delaminating the PA membrane. High aspect ratio nanowires of 60 nm diameter and 2.8 μm length were growth through the self-ordered PA membrane without any underlying metal coating i.e. without altering its optical properties. An average of 56% optical absorption (within 350 nm – 1400 nm wavelength) and a moderate photoluminescence was observed for the CdTe nanowires. Minor variation in the anodization process resulted into a non-uniform/branched PA template that enabled the formation of dense 3D hierarchical structures of CdTe using similar electrodeposition conditions as that used for CdTe nanowires. The hierarchical CdTe nanostructures exhibited very high total optical absorption of ∼90% within 350 nm – 1400 nm wavelength and a strong photoluminescence was also demonstrated that was almost 10 fold more intense than the CdTe nanowires.
Article 7 Reads 1 Citation Optical properties of a biomimetically prepared hierarchical structured polydimethyl siloxane template for potential app... Harsimran Singh Bindra, A B V Kiran Kumar, Ranu Nayak Published: 04 May 2017
Materials Research Express, doi: 10.1088/2053-1591/aa6365
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Article 0 Reads 1 Citation A Simple Low-Cost Approach of Fabricating Nanostructured Polydimethylsiloxane Layer for Application in Solar Cell Encaps... Divisha Rajput, Harsimran Singh Bindra, Arpita Saha, Ranu Na... Published: 01 July 2016
Advanced Science, Engineering and Medicine, doi: 10.1166/asem.2016.1829
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