Science Current Events | Science News | Brightsurf.com
 

With a simple coating, nanowires show a dramatic increase in efficiency and sensitivity

July 07, 2011
By applying a coating to individual silicon nanowires, researchers at Harvard and Berkeley have significantly improved the materials' efficiency and sensitivity.

The findings, published in the May 20, 2011, issue of Nano Letters, suggest that the coated wires hold promise for photodetectors and energy harvesting technologies like solar cells.

Due to a large surface-to-volume ratio, nanowires typically suffer from a high surface recombination rate, meaning that photogenerated charges recombine rather than being collected at the terminals. The carrier lifetime of a basic nanowire is shortened by four to five orders of magnitude, reducing the material's efficiency in applications like solar cells to a few percent.

"Nanowires have the potential to offer high energy conversion at low cost, yet their limited efficiency has held them back," says Kenneth Crozier, Associate Professor of Electrical Engineering at the Harvard School of Engineering and Applied Sciences (SEAS).

With their latest work, Crozier and his colleagues demonstrated what could be promising solution. Making fine-precision measurements on single nanowires coated with an amorphous silicon layer, the team showed a dramatic reduction in the surface recombination.

Surface passivation has long been used to promote efficiency in silicon chips. Until now, surface passivation of nanowires has been explored far less.

The creation of the coating that passivated the surfaces of the nanowires was a happy accident. During preparation of a batch of single-crystal silicon nanowires, the scientists conjecture, the small gold particles used to grow the nanowires became depleted. As a result, they think, the amorphous silicon coating was simply deposited onto the individual wires.

Instead of abandoning the batch, Crozier and his team decided to test it. Scanning photocurrent studies indicated, astoundingly, almost a hundred-fold reduction in surface recombination. Overall, the coated wires boasted a 90-fold increase in photosensitivity compared to uncoated ones.

Co-author Yaping Dan, a postdoctoral fellow in Crozier's lab who spearheaded the experiments, suggests that the reason for the increased efficiency is that the coating physically extends the broken atom bonds at the single-crystalline silicon surface. At the same time, the coating also may form a high-electric potential barrier at the interface, which confines the photogenerated charge carriers inside the single-crystalline silicon.

"As far as we know, scientists have not done these types of precision measurements of surface passivation at the level of single nanowires," says Crozier. "Simply by putting a thin layer of amorphous silicon onto a crystalline silicon nanowire reduces the surface recombination nearly two orders of magnitude. We think the work will address some of the disadvantages of nanowires but keep their advantages."

Due to their increased carrier lifetime, the researchers expect that their wires will offer higher energy conversion efficiency when used in solar cell devices.

###

Crozier and Dan's co-authors included Kwanyong Seo and Jhim H. Meza, both of SEAS, and Kuniharu Takei and Ali Javey at the University of California at Berkeley. The authors acknowledge the support of Zena Technologies. Fabrication work was carried out at the Center for Nanoscale Systems at Harvard (which is supported by the National Science Foundation).

Harvard University


Related Nanowires Current Events and Nanowires News Articles


A Crystal Wedding in the Nanocosmos
Researchers at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), the Vienna University of Technology and the Maria Curie-Skłodowska University Lublin have succeeded in embedding nearly perfect semiconductor crystals into a silicon nanowire. With this new method of producing hybrid nanowires, very fast and multi-functional processing units can be accommodated on a single chip in the future.

NUS scientists use low cost technique to improve properties and functions of nanomaterials
The challenges faced by researchers in modifying properties of nanomaterials for application in devices may be addressed by a simple technique, thanks to recent innovative studies conducted by scientists from the National University of Singapore (NUS).

Artificial enzyme mimics the natural detoxification mechanism in liver cells
Scientists at Johannes Gutenberg University Mainz (JGU) have discovered that molybdenum trioxide nanoparticles oxidize sulfite to sulfate in liver cells in analogy to the enzyme sulfite oxidase.

MIPT-based Researcher Predicts New State of Matter
A researcher with the Department of Electrodynamics of Complex Systems and Nanophotonics, Alexander Rozhkov, has presented theoretical calculations which indicate the possible existence of fermionic matter in apreviously unknown state - in the form ofaone-dimensional liquid, which cannot be described within the framework of existing models.

Molecular self-assembly scales up from nanometers to millimeters
To ensure the survival of Moore's law and the success of the nanoelectronics industry, alternative patterning techniques that offer advantages beyond conventional top-down patterning are aggressively being explored.

Nanowire-bridging transistors open way to next-generation electronics
A new approach to integrated circuits, combining atoms of semiconductor materials into nanowires and structures on top of silicon surfaces, shows promise for a new generation of fast, robust electronic and photonic devices.

Better solar cells, better LED light and vast optical possibilities
Changes at the atom level in nanowires offer vast possibilities for improvement of solar cells and LED light. NTNU-researchers have discovered that by tuning a small strain on single nanowires they can become more effective in LEDs and solar cells.

Domain walls in nanowires cleverly set in motion
Researchers at Johannes Gutenberg University Mainz (JGU) have achieved a major breakthrough in the development of methods of information processing in nanomagnets.

To bridge LEDs' green gap, scientists think small... really small
Nanostructures half the breadth of a DNA strand could improve the efficiency of light emitting diodes (LEDs), especially in the "green gap," a portion of the spectrum where LED efficiency plunges, simulations at the U.S. Department of Energy's National Energy Research Scientific Computing Center (NERSC) have shown.

USC Viterbi researchers developing cheap, better-performing lithium-ion batteries
Researchers at the USC Viterbi School of Engineering have improved the performance and capacity of lithium batteries by developing better-performing, cheaper materials for use in anodes and cathodes (negative and positive electrodes, respectively).
More Nanowires Current Events and Nanowires News Articles

Nanowire Field Effect Transistors: Principles and Applications

Nanowire Field Effect Transistors: Principles and Applications
by Dae Mann Kim (Editor), Yoon-Ha Jeong (Editor)


“Nanowire Field Effect Transistor: Basic Principles and Applications” places an emphasis on the application aspects of nanowire field effect transistors (NWFET). Device physics and electronics are discussed in a compact manner, together with the p-n junction diode and MOSFET, the former as an essential element in NWFET and the latter as a general background of the FET.
During this discussion, the photo-diode, solar cell, LED, LD, DRAM, flash EEPROM and sensors are highlighted to pave the way for similar applications of NWFET. Modeling is discussed in close analogy and comparison with MOSFETs. Contributors focus on processing, electrostatic discharge (ESD) and application of NWFET. This includes coverage of solar and memory cells, biological and chemical sensors, displays and...

Nanowires and Nanobelts: Materials, Properties and Devices. Volume 1: Metal and Semiconductor Nanowires

Nanowires and Nanobelts: Materials, Properties and Devices. Volume 1: Metal and Semiconductor Nanowires
by Zhong Lin Wang (Editor)


Nanowires, nanobelts, nanoribbons, nanorods . . . , are a new class of quasi-one­ dimensional materials that have been attracting a great research interest in the last few years. These non-carbon based materials have been demonstrated to exhibit superior electrical, optical, mechanical and thermal properties, and can be used as fundamen­ tal building blocks for nano-scale science and technology, ranging from chemical and biological sensors, field effect transistors to logic circuits. Nanocircuits built using semiconductor nanowires demonstrated were declared a "breakthrough in science" by Science magazine in 2001. Nature magazine recently published a report claiming that "Nanowires, nanorods, nanowhiskers, it does not matter what you call them, they are the hottest property in...

Wide Band Gap Semiconductor Nanowires for Optical Devices (ISTE)

Wide Band Gap Semiconductor Nanowires for Optical Devices (ISTE)
by Vincent Consonni (Editor), Guy Feuillet (Editor)


This book, the second of two volumes, describes heterostructures and optoelectronic devices made from GaN and ZnO nanowires.Over the last decade, the number of publications on GaN and ZnO nanowires has grown exponentially, in particular for their potential optical applications in LEDs, lasers, UV detectors or solar cells. So far, such applications are still in their infancy, which we analyze as being mostly due to a lack of understanding and control of the growth of nanowires and related heterostructures. Furthermore, dealing with two different but related semiconductors such as ZnO and GaN, but also with different chemical and physical synthesis methods, will bring valuable comparisons in order to gain a general approach for the growth of wide band gap nanowires applied to optical...

Handbook of Nanophysics: Nanotubes and Nanowires

Handbook of Nanophysics: Nanotubes and Nanowires
by Klaus D. Sattler (Editor)


Intensive research on fullerenes, nanoparticles, and quantum dots in the 1990s led to interest in nanotubes and nanowires in subsequent years. Handbook of Nanophysics: Nanotubes and Nanowires focuses on the fundamental physics and latest applications of these important nanoscale materials and structures. Each peer-reviewed chapter contains a broad-based introduction and enhances understanding of the state-of-the-art scientific content through fundamental equations and illustrations, some in color. This volume first covers key aspects of carbon nanotubes, including quantum and electron transport, isotope engineering, and fluid flow, before exploring inorganic nanotubes, such as spinel oxide nanotubes, magnetic nanotubes, and self-assembled peptide nanostructures. It then focuses on...

Nanoelectronics: Nanowires, Molecular Electronics, and Nanodevices

Nanoelectronics: Nanowires, Molecular Electronics, and Nanodevices
by Krzysztof Iniewski (Author)


The latest advances in nanoelectronics This definitive volume addresses the state of the art in nanoelectronics, covering nanowires, molecular electronics, and nanodevices. Written by global experts in the field, Nanoelectronics discusses cutting-edge techniques and emerging materials, such as carbon nanotubes and quantum dots. This pioneering work offers a comprehensive survey of nanofabrication options for use in next-generation technologies. Nanoelectronics covers: Electrical properties of metallic nanowires Electromigration defect nucleation in damascene copper interconnect lines Carbon nanotube interconnects in CMOS integrated circuits Printed organic electronics One-dimensional nanostructure-enabled chemical sensing Cross-section fabrication and analysis of nanoscale device...

Nanowires and Nanobelts: Materials, Properties and Devices: Volume 2: Nanowires and Nanobelts of Functional Materials

Nanowires and Nanobelts: Materials, Properties and Devices: Volume 2: Nanowires and Nanobelts of Functional Materials
by Zhong Lin Wang (Editor)


Nanowires, nanobelts, nanoribbons, nanorods…, are a new class of quasi-o- dimensional materials that have been attracting a great research interest in the last few years. These non-carbon based materials have been demonstrated to exhibit superior electrical, optical, mechanical and thermal properties, and can be used as fundam- tal building blocks for nano-scale science and technology, ranging from chemical and biological sensors, field effect transistors to logic circuits. Nanocircuits built using semiconductor nanowires demonstrated were declared a “breakthrough in science” by Science magazine in 2001. Nature magazine recently published a report claiming that “Nanowires, nanorods, nanowhiskers, it does not matter what you call them, they are the hottest property in...

Nanowires and Nanobelts: Materials, Properties and Devices (2 Volumes)

Nanowires and Nanobelts: Materials, Properties and Devices (2 Volumes)
by Zhong Lin Wang (Editor)


This two volume reference, Nanowires and Nanobelts: Materials, Properties and Devices, provides a comprehensive introduction to the field and reviews the current state of the research.
Volume 1, Metal and Semiconductor Nanowires covers a wide range of materials systems, from noble metals (such as Au, Ag, Cu), single element semiconductors (such as Si and Ge), compound semiconductors (such as InP, CdS and GaAs as well as heterostructures), nitrides (such as GaN and Si3N4) to carbides (such as SiC). The objective of this volume is to cover the synthesis, properties and device applications of nanowires based on metal and semiconductor materials. The volume starts with a review on novel electronic and optical nanodevices, nanosensors and logic circuits that have been built using...

  Quantum Dots and Nanowires
by Supriyo Bandyopadhyay and Hari Singh Nalwa (Author), Supriyo Bandyopadhyay (Editor), Hari Singh-Nalwa (Editor)


Quantum Dots and Nanowires provides coverage on various emerging aspects of quantum dots and nanowires. This book covers recent advances in physical and chemical synthetic approaches, processing and fabrication of semiconductor quantum-dot arrays, superlattices, self-assemblies, nanowires, nanotubes and nanobelts, computational modeling approaches, spectroscopic characterization, their unique electrical, optical, magnetic and physical properties associated with size effect, transport phenomena, quantum computing, and other potential applications. An essential resource for scientists, researchers, upper-level undergraduate and graduate students, and college and university professors working in the field of electrical and electronic engineering, materials science, solids tate physics,...

Nanosensors for Chemical and Biological Applications: Sensing with Nanotubes, Nanowires and Nanoparticles (Woodhead Publishing Series in Electronic and Optical Materials)

Nanosensors for Chemical and Biological Applications: Sensing with Nanotubes, Nanowires and Nanoparticles (Woodhead Publishing Series in Electronic and Optical Materials)
by Kevin C. Honeychurch (Editor)


Nano-scale materials are proving attractive for a new generation of devices, due to their unique properties. They are used to create fast-responding sensors with good sensitivity and selectivity for the detection of chemical species and biological agents. Nanosensors for Chemical and Biological Applications provides an overview of developments brought about by the application of nanotechnology for both chemical and biological sensor development. Part one addresses electrochemical nanosensors and their applications for enhanced biomedical sensing, including blood glucose and trace metal ion analysis. Part two goes on to discuss spectrographic nanosensors, with chapters on the use of nanoparticle sensors for biochemical and environmental sensing and other techniques for detecting...

Inorganic Nanowires: Applications, Properties, and Characterization (Nanomaterials and their Applications)

Inorganic Nanowires: Applications, Properties, and Characterization (Nanomaterials and their Applications)
by M. Meyyappan (Author), Mahendra K. Sunkara (Author)


Advances in nanofabrication, characterization tools, and the drive to commercialize nanotechnology products have contributed to the significant increase in research on inorganic nanowires (INWs). Yet few if any books provide the necessary comprehensive and coherent account of this important evolution. Presenting essential information on both popular and emerging varieties, Inorganic Nanowires: Applications, Properties, and Characterization addresses the growth, characterization, and properties of nanowires. Author Meyyappan is the director and senior scientist at Ames Center for Nanotechnology and a renowned leader in nanoscience and technology, and Sunkara is also a major contributor to nanowire literature. Their cutting-edge work is the basis for much of the current understanding in...

© 2014 BrightSurf.com