Preface

Quasi-one-dimensional nanoscale materials such as nanowires have been a research focus in the fields of material sciences and engineering in the last few decades. A series of books emphasizing the research areas of nanowires have been published by several scientific publishers. This book provides a review of the recent progress of nanowires and their wide range of applications, as well as the associated advancements in material synthesis and characterization.

Low-dimensional nanoscale materials exhibit promising applications in today's science and technology, due to their reduction in size, large surface-to-volume ratio, and novel properties resulting from quantum confinement effects. The significantly larger surface-to-volume ratio in nanostructures, compared with their bulk counterparts, leads to high sensitivity to surface effects and enables a new generation of technologies in research fields. Compared to other low-dimensional structures, such as zero-dimensional quantum dots (or nanoclusters) and two-dimensional nanosheets, one-dimensional nanowires demonstrate unique geometrical advantages that expedite the application of nanowires as bases of electronic devices, such as channels and interconnects. In such applications, the reduction in size of nanowires enables a faster speed and a greater power density, in addition to a reduced device form factor. Numerous conventional techniques established in traditional bulk devices are readily applicable to nanowire devices, which is expected to boost extensive applications of nanowires.

This book contains ten chapters divided into three sections: Oxide Nanowires, Group III–V Compounds, and Other Nanowires.

Section 1 examines recent progress in metal oxide nanowires, which include novel transition metal oxide nanowire field-effect transistors for biosensing, nanowires as building blocks for optoelectronic devices, and an advanced technique of glancing angle deposition for nanowire synthesis and their applications. Transition metal oxides, such as ZnO, CuO, TiO2, SnO2, and WO3, possess various advanced properties, for instance, resilient catalyst properties and large magnetoresistance coefficients. These exceptional properties are fundamentally correlated to the unfilled d-electrons in the transition metals. Transition metal oxide nanowires, combined with their unique size, geometrical effects, and stoichiometry engineering, are expected to reveal novel properties/applications and to play an important role in many different fields of science and technology. Chapter 1 provides a review of ZnO nanowire field-effect transistors and biosensors, emphasizing the different ways to improve the properties and performance of doped ZnO as a channel material. It suggests that top-down fabrication processes are preferred over bottom-up ones due to the former's enhanced flexibility of geometrical dimension control and capability of mass production. Chapter 2 focuses on two types of metal oxide nanowire arrays: the n-type eco-friendly and versatile ZnO and p-type highly stable CuO, using two straightforward and cost-effective preparation wet and dry methods of chemical synthesis in aqueous solution and thermal oxidation in air, respectively. Electronic devices based on single metal oxide nanowires were developed and analyzed in

**II**

**Chapter 8 135**

**Chapter 9 157**

**Chapter 10 173**

*by Jun-Sik Yoon, Jinsu Jeong, Seunghwan Lee, Junjong Lee and Rock-Hyun Baek*

Engineering the Color and the Donor-Acceptor Behavior in Nanowires:

Nanowires Integrated to Optical Waveguides *by Ricardo Téllez-Limón and Rafael Salas-Montiel*

Blend Versus Coaxial Geometry *by Mohamed Mbarek and Kamel Alimi*

Gate-All-Around FETs: Nanowire and Nanosheet Structure

terms of electrical characterization. Chapter 3 gives reviews the synthesis of metal oxide nanowires and axial hetero-structure nanowire arrays using the technique of glancing angle deposition and discusses many related applications such as photodetector and wettability applications. It is shown that the glancing angle deposition technique is simple, cost-effective, and catalytic free with many advantages compared to other methods.

Section 2 mainly focuses on group III–V compounds, including GaN for photoelectrochemical water splitting, InGaN nanowires for photovoltaic applications, and in situ techniques facilitating understanding of GaAs nanowire growth. Si is one of the most known bulk semiconductors and the logic device basis-CMOS structure is largely based on Si material. However, group III–V semiconductors, such as GaN, GaAs, and InN, provide numerous property advantages over Si. They demonstrate outstanding electronic and optical properties, for instance, direct band gap, increased carrier mobility, and low exciton binding energy, which give these semiconductors great potential for use in optoelectronic and microelectronic fields. Chapter 4 shows that GaN is a promising photoelectrode for photoelectrochemical water spitting reaction due to its tunable band gap, favorable band edge positions, and extraordinary stability. Chapter 5 presents a comparative analysis of different structural formats of InGaN, such as planar, nanodisk, and core-shell-shell nanowires, for their performances as potential photovoltaic material and concludes that nanowire-type structure displays a better performance. Chapter 6 introduces advanced in situ techniques to provide direct interpretation and time-resolved observation of the growth mechanism of nanowires, which allows better control of nanowire growth for specific applications.

Section 3 contributes to the fundamental understanding of other nanowire structures including basic Si nanowires, metallic wires, and complex geometrical nanowires. Chapter 7 reports a growth method of indium-catalyzed Si nanowires via vapor-liquid-solid mode for nanoscale device applications, with good control of scaling down the diameter of the Si nanowire and an enhanced growth density of nanowires. In addition to the semiconductor nanowires already mentioned, Chapter 8 focuses on a study of a hybridization design between plasmonic and photonic-guided modes in periodic arrays of metallic nanowires integrated on top of dielectric waveguides. The chapter aims to stimulate further research efforts in the development of integrated hybrid photonic–plasmonic devices in the research community. The last two chapters introduce complex geometrical nanowires. Chapter 9 provides a thorough study on three-nanometer node gate-all-around field-effect transistors based on two types of nanostructures: nanowire and nanosheet. The study suggests that nanowire field-effect transistors have better performance compared to the fin-shaped and nanosheet transistors at low power applications. Chapter 10 suggests a method to engineer an enhanced donor-acceptor behavior in blending and core-shell nanowires. It describes a synthesis method of poly (para-phenylene-vinylene) PPV (electron donor) and poly (vinyl-carbazole) PVK (good hole transport) nanowires, and its core-shell architecture bases on PPV and PVK polymers. This study found that the core-shell morphology based on PVK and PPV polymers showed an amplified emission of PPV intensity by adding PVK. The chapter provides a way to develop alternative in-solution processing techniques to manage the local organization of donor-acceptor systems at the scale of the exciton diffusion length.

**V**

Finally, I would like to acknowledge all the contributors for their hard work. I am also grateful for the opportunity provided by IntechOpen, such that this interesting topic can be reviewed and shared among the research community. I would also like to express my appreciation for all the excellent editing work done by the IntechOpen staff. At last, my special acknowledgment goes to Author Service Manager Josip Knapić for all of his encouragement, patience, and kindness during

**Dr. Xihong Peng**

Arizona State University, Polytechnic Campus, Arizona, United States

College of Integrative Sciences and Arts,

the editing process.

Finally, I would like to acknowledge all the contributors for their hard work. I am also grateful for the opportunity provided by IntechOpen, such that this interesting topic can be reviewed and shared among the research community. I would also like to express my appreciation for all the excellent editing work done by the IntechOpen staff. At last, my special acknowledgment goes to Author Service Manager Josip Knapić for all of his encouragement, patience, and kindness during the editing process.

> **Dr. Xihong Peng** College of Integrative Sciences and Arts, Arizona State University, Polytechnic Campus, Arizona, United States

**IV**

terms of electrical characterization. Chapter 3 gives reviews the synthesis of metal oxide nanowires and axial hetero-structure nanowire arrays using the technique of glancing angle deposition and discusses many related applications such as photodetector and wettability applications. It is shown that the glancing angle deposition technique is simple, cost-effective, and catalytic free with many advantages

Section 2 mainly focuses on group III–V compounds, including GaN for photoelectrochemical water splitting, InGaN nanowires for photovoltaic applications, and in situ techniques facilitating understanding of GaAs nanowire growth. Si is one of the most known bulk semiconductors and the logic device basis-CMOS structure is largely based on Si material. However, group III–V semiconductors, such as GaN, GaAs, and InN, provide numerous property advantages over Si. They demonstrate outstanding electronic and optical properties, for instance, direct band gap, increased carrier mobility, and low exciton binding energy, which give these semiconductors great potential for use in optoelectronic and microelectronic fields. Chapter 4 shows that GaN is a promising photoelectrode for photoelectrochemical water spitting reaction due to its tunable band gap, favorable band edge positions, and extraordinary stability. Chapter 5 presents a comparative analysis of different structural formats of InGaN, such as planar, nanodisk, and core-shell-shell nanowires, for their performances as potential photovoltaic material and concludes that nanowire-type structure displays a better performance. Chapter 6 introduces advanced in situ techniques to provide direct interpretation and time-resolved observation of the growth mechanism of nanowires, which allows better control of

Section 3 contributes to the fundamental understanding of other nanowire structures including basic Si nanowires, metallic wires, and complex geometrical nanowires. Chapter 7 reports a growth method of indium-catalyzed Si nanowires via vapor-liquid-solid mode for nanoscale device applications, with good control of scaling down the diameter of the Si nanowire and an enhanced growth density of nanowires. In addition to the semiconductor nanowires already mentioned, Chapter 8 focuses on a study of a hybridization design between plasmonic and photonic-guided modes in periodic arrays of metallic nanowires integrated on top of dielectric waveguides. The chapter aims to stimulate further research efforts in the development of integrated hybrid photonic–plasmonic devices in the research community. The last two chapters introduce complex geometrical nanowires. Chapter 9 provides a thorough study on three-nanometer node gate-all-around field-effect transistors based on two types of nanostructures: nanowire and nanosheet. The study suggests that nanowire field-effect transistors have better performance compared to the fin-shaped and nanosheet transistors at low power applications. Chapter 10 suggests a method to engineer an enhanced donor-acceptor behavior in blending and core-shell nanowires. It describes a synthesis method of poly (para-phenylene-vinylene) PPV (electron donor) and poly (vinyl-carbazole) PVK (good hole transport) nanowires, and its core-shell architecture bases on PPV and PVK polymers. This study found that the core-shell morphology based on PVK and PPV polymers showed an amplified emission of PPV intensity by adding PVK. The chapter provides a way to develop alternative in-solution processing techniques to manage the local organization of donor-acceptor systems

compared to other methods.

nanowire growth for specific applications.

at the scale of the exciton diffusion length.

**1**

Section 1

Oxide Nanowires

Section 1 Oxide Nanowires

**3**

**Chapter 1**

Review

**Abstract**

also reviewed.

**1. Introduction**

Related to similar IIb

*Nonofo Mathiba Jack Ditshego*

ZnO Nanowire Field-Effect

Transistor for Biosensing: A

**Keywords:** zinc oxide (ZnO), semiconductor device, nanosensor,

time period shown on p-type ZnO was a few months [5–14].

(300 K) = (3.365 ± 0.005) eV]. It belongs to the group of II<sup>b</sup>

which corresponds to 4.2 × 1022 ZnO molecules per cm−3 [1, 2].

ZnO is a wide bandgap semiconductor [e.g., (0 K) = (3.441 ± 0.003) eV;

GaN, and InSb) semiconductors, it has comparatively strong polar binding and large exciton binding energy of (59.5 ± 0.5) meV. Its density is 5.6 g cm−3, a value

ductors which crystalize exclusively in the hexagonal wurtzite-type structure. The lattice parameters of the wurtzite crystal structure are: *a* = 3.24 Å and *c* = 5.21 Å.



nanowire field-effect transistor (NWFET), biosensors, growth techniques

Zinc oxide (ZnO) material has been known as a semiconductor for over 70 years, with some of the first literature being reported as early as in 1944 [1]. It was never put to use like other semiconductors (GaN, Si) because it is difficult to dope. The past 19 years have seen a revival on the research and use of material because of new and emerging ways of doping it. The material is naturally n-type [1–4], and by controlling the conditions of growth, the donor concentration can be controlled. The growth conditions include temperature, diethyl zinc (DEZ) reactant, O2 or H2O reactant, and pressure. P-type material [1–4] is difficult to grow and tends to slowly revert back to n-type. Researchers [5–14] who managed to deposit the p-type material have shown that it converts back to n-type within a few days. Maximum

The last 19 years have seen intense research made on zinc oxide (ZnO) material, mainly due to the ability of converting the natural n-type material into p-type. For a long time, the p-type state was impossible to attain and maintain. This chapter focuses on ways of improving the doped ZnO material which acts as a channel for nanowire field-effect transistor (NWFET) and biosensor. The biosensor has specific binding which is called functionalization that is achieved by attaching a variety of compounds on the designated sensing area. Reference electrodes and buffers are used as controllers. Top-down fabrication processes are preferred over bottom-up because they pave way for mass production. Different growth techniques are reviewed and discussed. Strengths and weaknesses of the FET and sensor are
