Nanowires – P-Type Vs N-Type, Electronic Properties, Modulus of Elasticity


Among many other topics, this article will discuss the p-type vs. n-type of nanowires. Also, it will provide the Electronic properties, Modulus of elasticity, Applications, and Photonics.

p-type vs n-type

Compared with n-type nanowires, p-type nanowires are harder to manufacture. The key reason is the difference in the number of dopants that are required. It is known that p-type doping can increase the conductivity of semiconductor nanowires. However, the characterization of such nanowires is still elusive. In addition to their conductive properties, p-type nanowires can be used for energy conversion.

A team of scientists from Beijing Normal University, Chinse University of Hong Kong, and the Beijing Computational Science Research Center have published a paper in the National Science Review. Their research used microscopic simulations to determine the effects of axial twist on the distribution of p-type and n-type dopants in the nanowire. They discovered that a twist induced inhomogeneous shear strain can lead to the separation of p-type and n-type.

A p-n junction with a positive gate voltage is the best choice for energy conversion. It is important to recognize that different doping elements are considered optimal.

Modulus of elasticity

Using the in situ TEM technique, the elastic properties of Silver nanowires are studied. Their elasticity is investigated to find out what mechanisms can reduce thermal conductivity. This study will also guide future designs of artificial nanostructures for thermoelectric applications.

The elastic limit of single-crystalline Si nanowires was investigated. It is found that the modulus of elasticity is close to bulk silicon, and is also independent of the diameter. Using this method, the critical compression force for axial buckling can be calculated. Several studies have investigated the size and weight dependence of various elastic properties. However, there is little consensus on how to interpret these results.

The smallest nanowires are 35 nm in diameter. However, the size effect is not apparent for wires less than 25 nm in diameter. In a cyclic stretching experiment, large strains are observed, but the actual length of the nanowire is restored immediately after the stretch. This shows that the size effect is not necessarily an important factor.

The best way to measure the modulus of elasticity is by analyzing a stress-strain curve. In this technique, the total energy of the nanowire is calculated as the sum of the bulk and surface materials. It is also possible to measure the transverse deflection of the nanowire.

Electronic properties

Detailed electronic properties of nanowires are required for the design and optimization of optoelectronic devices. In particular, III-V semiconducting nanowires have to be characterized before they can be integrated into nanoelectronic devices. These devices include photovoltaics, single electron transistors, and memory cells. Nanowires have potential uses in next-generation technologies.

Theoretical and experimental studies have investigated the effects of intrawire defects on the optical and electronic properties of nanowires. For example, Ohnishi and Kondo discovered that double strand conductance is twice that of single strand conductance. This suggests that the number of strands may have a significant impact on the conductance of nanowires.

A common method to monitor structural changes in nanowires is to analyze the atomic volume. The atomic volume increases dramatically when structural changes occur. Using this approach, Ohnishi and Kondo observed that a decrease in the number of 1421 bond pairs in a cluster of wires indicates a melting of the nanowire.

In addition to the above approaches, molecular dynamics (MD)-based methods can be used to optimize the structure of nanowires. These methods can also be used to monitor structural changes in nanowires.

Applications in photonics

During the last decade, there has been a world-wide research effort in photonics aiming to rationally integrate different functions. One such function is light emission, integrating light propagation and light detection. The integration of light generation and detection is advantageous for on-chip light signal processing.

Several vertically aligned photonic nanowires have been developed for several applications. Vertical nanowires exhibit efficient light absorption and wavelength selectivity. They have been used for multispectral imaging systems and artificial retinas. Also, they  convert light to photocurrent. They are used in light-emitting diodes (LEDs). They are also commercially manufacturable nanostructures with low fabrication cost.

These nanowires can be manufactured with various fabrication techniques. They can be manufactured with bottom-up or top-down methods. The main fabrication methods are etching, vapor-liquid-solid (VLS) method and metal-assisted chemical etching (MAEC). In addition, structure engineering is also carried out through additional shaping steps.

Typical geometric features of vertical nanowire can be controlled through masking, etching and vapor-liquid-solid (VLS) methods. Moreover, nanowires can be controlled through diameter modulation. As the nanowire diameter increases, its reflection spectra shift to a longer wavelength. Moreover, the optical absorption efficiency of Si nanowire arrays increases with the decreasing modulation period. This makes them ideal for on-chip light signal processing.

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