Considerable attention has been devoted to silicon (Si) nanowire arrays for photovoltaic energy conversion applications. Vertical arrays of Si nanowires with radial p-n/p-i-n junctions decouple the light absorption direction and photogenerated carrier collection direction, which enables the use of lower-quality Si materials without sacrificing device performance. Moreover, vapor-liquid-solid (VLS) technique offers the possibility of growing Si nanowires on inexpensive substrates such as glass or metal foil instead of crystalline Si substrates, which can reduce the cost of Si-based solar cells. The radial junction dark current plays an important role in the photovoltaic performance of these devices because Si nanowire arrays have significantly larger electrically active junction area relative to illuminated area of the solar cell. Previously reported Si nanowire solar cell devices suffer from the high dark current, low open circuit voltage, and low energy conversion efficiency. Therefore, it is necessary to understand the mechanisms responsible for the high dark current in radial junction Si nanowires and to develop strategies to improve junction properties through optimization of the VLS growth and shell coating processes. This thesis reports on the electrical and photovoltaic properties of individual radial junction Si nanowire devices to evaluate the effectiveness of different nanowire VLS growth and shell coating conditions. A process was developed to fabricate radial p+-n+ and p+-i-n+ junction Si nanowire devices that combines deterministic bottom-up assembly of individual nanowires with conventional top-down device nanofabrication. The effect of the metal catalyst, coating morphology and shell layer passivation were investigated in this research. In chapter 3, VLS growth using Al as catalyst was used to synthesize the p-type Si nanowires. Radial junctions were formed by low pressure chemical vapor deposition (LPCVD) of n+ or i-n+ Si layers on the p-type nanowires. In chapter 4, p-type nanowires were synthesized by VLS growth using Au as catalyst. The n-type shells were deposited by LPCVD at different growth temperatures to investigate the effect of coating morphology and pretreatment conditions on the electrical properties of the junctions. In chapter 5, radial heterojunction with intrinsic thin-layer (HIT) nanowire junctions were formed by plasma enhanced chemical vapor deposition (PECVD) of amorphous hydrogenated Si (a-Si:H) i-n layers on Au-catalyzed VLS-grown p-type wires. The electrical properties and photovoltaic performance of devices fabricated from individual radial junction nanowires were evaluated by current-voltage (I-V) measurement in the dark and under Air Mass 1.5 Global (AM 1.5G) illumination. Variable-temperature I-V measurements were used to analyze the mechanisms responsible for the dark current and to determine the conditions that produce the highest quality radial nanowire junctions for photovoltaic applications.

A timely reference from leading experts on semiconductor nanowires and their applications.

Semiconductor nanowires promise to provide the building blocks for a new generation of nanoscale electronic and optoelectronic devices. Semiconductor Nanowires: Materials, Synthesis, Characterization and Applications covers advanced materials for nanowires, the growth and synthesis of semiconductor nanowires—including methods such as solution growth, MOVPE, MBE, and self-organization. Characterizing the properties of semiconductor nanowires is covered in chapters describing studies using TEM, SPM, and Raman scattering. Applications of semiconductor nanowires are discussed in chapters focusing on solar cells, battery electrodes, sensors, optoelectronics and biology. - Explores a selection of advanced materials for semiconductor nanowires - Outlines key techniques for the property assessment and characterization of semiconductor nanowires - Covers a broad range of applications across a number of fields

"Semiconductor nanowires exhibit novel electronic and optical properties due to their unique one-dimensional structure and quantum confinement effects. In particular, III-V semiconductor nanowires have been of great scientific and technological interest fo"

Semiconductor Nanowires: Part B, and Volume 94 in the Semiconductor and Semimetals series, focuses on semiconductor nanowires. - Includes experts contributors who review the most important recent literature - Contains a broad view, including examination of semiconductor nanowires

This book covers virtually all aspects of semiconductor nanowires, from growth to related applications, in detail. First, it addresses nanowires’ growth mechanism, one of the most important topics at the forefront of nanowire research. The focus then shifts to surface functionalization: nanowires have a high surface-to-volume ratio and thus are well-suited to surface modification, which effectively functionalizes them. The book also discusses the latest advances in the study of impurity doping, a crucial process in nanowires. In addition, considerable attention is paid to characterization techniques such as nanoscale and in situ methods, which are indispensable for understanding the novel properties of nanowires. Theoretical calculations are also essential to understanding nanowires’ characteristics, particularly those that derive directly from their special nature as one-dimensional nanoscale structures. In closing, the book considers future applications of nanowire structures in devices such as FETs and lasers.

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 individual nanowires as building blocks. Then, the theoretical background for electrical properties and mechanical properties of nanowires is given. The molecular nanowires, their quantized conductance, and metallic nanowires synthesized by chemical technique will be introduced next. Finally, the volume covers the synthesis and properties of semiconductor and nitrides nanowires.

Nanowires are attracting wide scientific interest due to the unique properties associated with their one-dimensional geometry. Developments in the understanding of the fundamental principles of the nanowire growth mechanisms and mastering functionalization provide tools to control crystal structure, morphology, and the interactions at the material interface, and create characteristics that are superior to those of planar geometries. This book provides a comprehensive overview of the most important developments in the field of nanowires, starting from their synthesis, discussing properties, and finalizing with nanowire applications. The book consists of two parts: the first is devoted to the synthesis of nanowires and characterization, and the second investigates the properties of nanowires and their applications in future devices.