It is conventionally assumed that the growth of monodisperse colloidal nanocrystals requires a temporally discrete nucleation followed by monomer attachment onto the existing nuclei. However, recent studies have reported violations of this classical growth model, and have suggested that inter-particle interactions are also involved during the growth. Mechanisms of nanocrystal growth still remain controversial. Using in situ transmission electron microscopy, we show that platinum nanocrystals can grow either by monomer attachment from solution onto the existing particles or by coalescence between the particles. Surprisingly, an initially broad size distribution of the nanocrystals can spontaneously narrow. We suggest that nanocrystals take different pathways of growth based on their size- and morphology-dependent internal energies. These observations are expected to be highly relevant for other nanocrystal systems.

Observation of Single Colloidal Platinum Nanocrystal Growth Trajectories

Chalcogenide phase change materials based on germanium-antimony-tellurides (GST-PCMs) have shown outstanding properties in non-volatile memory (NVM) technologies due to their high write and read speeds, reversible phase transition, high degree of scalability, low power consumption, good data retention, and multi-level storage capability. However, GST-based PCMs have shown recent promise in other domains, such as in spatial light modulation, beam steering, and neuromorphic computing. This paper reviews the progress in GST-based PCMs and methods for improving the performance within the context of new applications that have come to light in recent years.

https://www.mdpi.com/2076-3417/9/3/530/pdf

A Review of Germanium-Antimony-Telluride Phase Change Materials for Non-Volatile Memories and Optical Modulators

Chloride-Based CVD Growth of Silicon Carbide for Electronic Applications Henrik Pedersen,* Stefano Leone, Olof Kordina, Anne Henry, Shin-ichi Nishizawa, Yaroslav Koshka, and Erik Janz en Department of Physics, Chemistry and Biology, Link€oping University, SE-581 83 Link€oping, Sweden National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan Department of Electrical and Computer Engineering, Mississippi State University, Mississippi State, Mississippi 39762, United States

Chloride-based CVD growth of silicon carbide for electronic applications.

From thin film to bulk 3C-SiC growth: Understanding the mechanism of defects reduction

For a long time now, 3C-SiC has attracted attention of the semiconductor community due to its very interesting properties. The lack of commercial 3C-SiC seeds for epitaxy has forced researchers to prospect for different host materials in order to grow heteroepitaxial thin layers. Because of the obvious economical and technical advantages, silicon is a very attractive substrate so that more than 90% of the thin 3C-SiC heteroepitaxial films are grown on such seed. However, the obstacles to overcome, mainly lattice and thermal mismatch, are challenging. This article reviews the numerous attempts for growing high quality 3C-SiC heteroepitaxial layers on silicon substrate. The various aspects of the heteroepitaxial growth, from substrate carbonization to epitaxy, are discussed as a function of growth parameters. The difficulties encountered and the proposed solutions are described. Perspectives of this heteroepitaxial system are proposed.

3C-SiC Heteroepitaxial Growth on Silicon: The Quest for Holy Grail

The heteroepitaxial growth of 3C-SiC films on on-axis (100), (110), and (111) Si oriented substrates has been investigated. A multistep growth process using low-pressure chemical vapor deposition with trichlorosilane as the silicon precursor was conducted at a growth temperature of 1350 °C. X-ray diffraction analysis (θ-2θ and polar figure) and numerical simulation have been shown to be a suitable method to investigate and understand the SiC film structural properties for each substrate orientation. Epitaxial SiC films with first order twins, at least for growth on (100) and (111) Si, were obtained. SiC growth on (110) Si, on the other hand, showed a change in the growth direction by the observation of first and second order twins from the ⟨110⟩ to ⟨111⟩ direction. This is due to the high growth rate of (110) 3C-SiC/(110) Si heteroepitaxial system which encourages the SiC film to grow in a direction with a higher packing density. It was observed that the 3C-SiC surface morphology and average residual stre...

Heteroepitaxy of 3C-SiC on different on-axis oriented silicon substrates

SiC is a candidate material for microelectromechanical and nanoelectromechanical systems, but the high residual stress created during the film grow limits the development of the material for these applications. To understand the stress relaxation mechanism in hetero-epitaxial 3C-SiC films, different micromachined free-standing structures have been realized. In this paper, assisted by finite-element method (FEM), a micromachined planar rotating probe was developed for residual stress analysis to split the stress into the following two components: 1) the gradient residual stress (σ1) related to the film defects and 2) the uniform stress (σ0) related to the substrate. Transmission electron microscopy characterization studies about the defect formation and the defect evolution as a function of thickness on 3C-SiC on the Si substrate revealed the problems due to the incorrect linear stress approximation in a heteroepitaxial thin film. With FEM, an exponential approximation of the stress relationship was studied, yielding a better fit with the experimental data. This paper shows that the new approximation of the total residual stress function reduces the actual disagreement between experimental and simulation data.

Advanced Residual Stress Analysis and FEM Simulation on Heteroepitaxial 3C–SiC for MEMS Application

Cubic (111)-oriented silicon carbide (3C-SiC) heteroepitaxy on (110) silicon substrate was performed by low pressure chemical vapor deposition. A comparison with the previous work by Nishiguchi et al. [Appl. Phy. Lett. 84, 3082 (2004)] shows that the relationship (110)Si∥(111) 3C-SiC could be misleading. Based on x-ray diffraction pole figures and numerical simulations, we prove that this relationship is due to the formation of second order twins during the initial stages of growth. This analysis also reveals that the crystal starts to grow with a misalignment of 3.5° along the ⟨002⟩ Si direction to adapt the mismatch of lattice parameters.

Heteroepitaxial growth of (111) 3C-SiC on (110) Si substrate by second order twins

This paper reports the electrooptical characteristics of ultraviolet light-sensitive 4H-SiC p $^{+} $ -n junction photodiodes obtained by aluminium (Al) ion implantation on low-doped n-type epilayers. A low dark current density ( $ at $-$ 100 V) was measured on 1- $\hbox{mm}^{2}$ area devices up to 90 $^{\circ}\hbox{C} $ . A peak responsivity of 0.11 A/W at 280 nm corresponding to a quantum efficiency of about 50% and a visible blindness $>\ 10^{3} $ were demonstrated. The absence of optically active defects and nitrogen donor–aluminum acceptor pair recombination centers was monitored by optical measurements in the visible range.

G. D'Arrigo

Papers

Heteroepitaxy of 3C-SiC on different on-axis oriented silicon substrates

Advanced Residual Stress Analysis and FEM Simulation on Heteroepitaxial 3C–SiC for MEMS Application

Heteroepitaxial growth of (111) 3C-SiC on (110) Si substrate by second order twins

Visible Blind 4H-SiC P $^{+}$ -N UV Photodiode Obtained by Al Implantation

Stress fields analysis in 3C–SiC free-standing microstructures by micro-Raman spectroscopy