Si Nanoribbons Research Articles

Elastic and plastic deformation of graphene, silicene, and boron nitride honeycomb nanoribbons under uniaxial tension: A first-principles density-functional theory study

This study of elastic and plastic deformation of graphene, silicene, and boron nitride (BN) honeycomb nanoribbons under uniaxial tension determines their elastic constants and reveals interesting features. In the course of stretching in the elastic range, the electronic and magnetic properties can be strongly modified. In particular, it is shown that the band gap of a specific armchair nanoribbon is closed under strain and highest valance and lowest conduction bands are linearized. This way, the massless Dirac fermion behavior can be attained even in a semiconducting nanoribbon. Under plastic deformation, the honeycomb structure changes irreversibly and offers a number of new structures and functionalities. Cagelike structures, even suspended atomic chains can be derived between two honeycomb flakes. Present work elaborates on the recent experiments [C. Jin, H. Lan, L. Peng, K. Suenaga, and S. Iijima, Phys. Rev. Lett. 102, 205501 (2009)] deriving carbon chains from graphene. Furthermore, the similar formations of atomic chains from BN and Si nanoribbons are predicted.

Crossbar heterojunction field effect transistors of CdSe:In nanowires and Si nanoribbons

Crossbar heterojunction arrays of n-CdSe:In nanowires (NWs) and p-Si nanoribbons (NRs) were built by ac electrical field-directed assembly. The junctions showed significant rectifying characteristics. With the p-Si NRs as gates, the junctions function as junction field effect transistors (JFETs) with high stability and reproducibility in performance. A small variation in gate voltage from −2 to −1 V was demonstrated to manipulate the current in n-CdSe:In NW channels by a factor near 103. The JFETs also showed a subthreshold swing value (67 mV/dec) approaching the theoretical limit (60 mV/dec), suggesting the great application potentials of the junctions in integrated nanoelectronics.

Confined VLS growth and structural characterization of silicon nanoribbons

Confined VLS growth is proposed to produce single crystalline silicon (c-Si) film over an amorphous oxide layer, without crystalline seed. The guided growth of Si nanoribbons (NRs) is successfully demonstrated and characterized using several electron microscopy techniques. First, VLS growth is studied on a plane substrate covered by gold (Au) patterned parallelepipedic ingots of several dimensions. In this unconstrained growth condition, c-Si nanowires (NWs) are synthesized with controlled position but random orientation on an amorphous substrate. Subsequently, it is demonstrated that VLS growth in the spatial confinement of a cavity produces nanometer-thick c-Si blades over a micron area scale with well-controlled localization. The nature of grown silicon layers is characterized by Scanning Electron Microscopy (SEM), Electron Backscattered Diffraction (EBSD) and Scanning Transmission Electron Microscopy (STEM) to analyze its crystallinity and to check the impact of the confining cavity walls on the purity of grown silicon. This technique opens the way for the fabrication of stacked active silicon layers isolated from each other useful for 3D CMOS integration.

Confined and guided catalytic growth of crystalline silicon films on a dielectric substrate

This paper presents the synthesis of epitaxial silicon (Si) nanoblades of controlled dimensions (thickness 50nm, width 200nm to 2μm) obtained by catalytic growth in a tunnel of confinement. The fabrication of horizontal cavities containing the catalyst slug is first described to show how the tunnel empty space is formed using an amorphous germanium sacrificial layer. These cavities served as a template to guide VLS (Vapor-Liquid-Solid) growth of crystalline Si standing on an amorphous substrate. The resulting self-assembled Si nanoribbons can be regarded as localized silicon-on-insulator (SOI) film that can be reproduced in the vertical direction to enable three-dimensional integration. The nature of the grown silicon film is characterized by scanning and transmission electron microscopy (SEM and TEM) as well as by electron backscattered diffraction (EBSD).

Mechano-electronic Superlattices in Silicon Nanoribbons

Significant new mechanical and electronic phenomena can arise in single-crystal semiconductors when their thickness reaches nanometer dimensions, where the two surfaces of the crystal are physically close enough to each other that what happens at one surface influences what happens at the other. We show experimentally that, in silicon nanomembranes, through-membrane elastic interactions cause the double-sided ordering of epitaxially grown nanostressors that locally and periodically highly strains the membrane, leading to a strain lattice. Because strain influences band structure, we create a periodic band gap modulation, up to 20% of the band gap, effectively an electronic superlattice. Our calculations demonstrate that discrete minibands can form in the potential wells of an electronic superlattice generated by Ge nanostressors on a sufficiently thin Si(001) nanomembrane at the temperature of 77 K. We predict that it is possible to observe discrete minibands in Si nanoribbons at room temperature if nanostressors of a different material are grown.

Mechanics of precisely controlled thin film buckling on elastomeric substrate

Stretchable electronics has many important and emerging applications. Sun et al. [Nature Nanotech. 1, 201 (2006)] recently demonstrated stretchable electronics based on precisely controlled buckle geometries in GaAs and Si nanoribbons on elastomeric substrates. A nonlinear buckling model is presented in this letter to study the mechanics of this type of thin film/substrate system. An analytical solution is obtained for the buckling geometry (wavelength and amplitude) and the maximum strain in buckled thin film. This solution agrees very well with the experiments, and shows explicitly how buckling can significantly reduce the thin film strain to achieve the system stretchability.

From Si Source Gas Directly to Positioned, Electrically Contacted Si Nanowires: The Self-Assembling “Grow-in-Place” Approach

Our grow-in-place approach to Si nanowire devices uses a silicon precursor gas (e.g., SiH 4 ) to directly produce self-assembled, electrically contacted, crystalline Si nanowires without any intervening silicon material formation or collection/positioning steps. The approach uses the vapor-liquid-solid (VLS) growth mechanism and lithographically fabricated, permanent, nanochannel growth templates to control the size, shape, orientation, and positioning of the nanowires and ribbons. These horizontal templates are an integral component of the final devices and provide contacts, interconnects, and passivation/encapsulation. The approach results in self-assembly of the Si nanowires (SiNWs) and nanoribbons (SiNRs) into interconnected devices without any pick-and-place or printing steps, thereby avoiding the most serious problems encountered in process control, assembly, contacting, and integration of SiNWs and SiNRs for IC applications. As an initial demonstration of our approach, we have fabricated SiNW and SiNR resistors with built-in electrical contacts and encapsulation and report conductivity measurements.