Accueil > Recherche > Matériaux nanostructurés > Les matériaux
Les matériaux
Amorphous & Polymorphous Silicon
For information on internships, doctoral studies, post-doctoral positions, or collaborations, please contact Prof. Pere Roca i Cabarrocas
Nanocrystalline Silicon
For information on internships, doctoral studies, post-doctoral positions, or collaborations, please contact Prof. Pere Roca i Cabarrocas
Epitaxy at 200°C
Silicon Nanowires
- Research topics and motivations:
1D silicon nanowires (SiNWs) are widely recognized as essentail building blocks for new generations of high-efficiency solar cells as well as high mobility field effect transistors. At LPICM we focus on producing silicon nanowires in a cost-efficient and CMOS-compatible approach. We emphasize the ability of in-situ fabrication and integration of SiNW based devices in a conventional plasma enhanced chemical vapor deposition (PECVD) system.
Two distinctive growth strategies of SiNW growth are pursued:
à Vertical SiNWs produced via a plasma-assisted vapor-liquid-solid (VLS) growth mode, catalyzed by low melting-temperature catalysts (tin and indium), aiming for SiNW radial junction solar cells or photonic applications; à Lateral SiNWs produced via a newly discovered in-plane solid-liquid-solid (IPSLS) growth mode for large-scale implementation of growth-in-place SiNW thin film transistors, and sensors, in a fully compatible CMOS process.
- Related research interests
1. Developing new understanding and insight into the growth mechanism and kinetic behavior, for achieving effective morphology, structure and position control.
2. Growth and morphology control of related semiconductor nanowires, as well as epitaxial hetero-junction structure.
For information on internships, doctoral studies, post-doctoral positions, or collaborations, please contact Dr Linwei YU
Dielectrics
Figure 1. MDECR plasma Ar discharge in the deposition chamber
Our Dielectric Thin Films are deposited by microwave (2.45 GHz) excited Plasma Enhanced Chemical Vapor Deposition. We combine the microwave excitation with a static magnetic field, which has the benefits of producing denser plasmas and confining the energetic electrons in the discharge. Indeed, the electrons are accelerated by the microwave electric field but also turned by the Lorentz force associated with the magnetic field. At a frequency of 2.45 GHz, a magnetic field strength of 875 Gauss ensures the optimal coupling between the electric and magnetic fields. This effect is known as Electron Cyclotron Resonance (ECR). In the deposition system, the magnet-antenna structures are distributed in space matrix-like, thus the nomenclature MDECR. Credit for the invention of such arrangement belongs to the French plasma physicist Dr. Jacques Pelletier from Grenoble.
The electronic density in the MDECR plasma can be up to 2 orders of magnitude higher that in the case of RF CCP plasmas (RF inductively coupled plasma produce comparable plasma density), and consequently, the dissociation of the precursor gas is very high. Therefore, very high deposition rates may be obtained (12nm/s for good quality SiO2). Another consequence is that in this kind of plasma, large ion flux can be obtained without external substrate bias, which allows us to obtain very dense, bulk-like, films. This is true also for room temperature depositions, which makes the deposition of Dielectric Thin Films on plastic possible.
Figure 3. Design and measured transmission for Bragg reflector shown above
This research has been developed in a close collaboration with industry: L'Air Liquide in the period 1992-2001, with Saint Gobain Sekurit 1997-2001, with American company OCLI from the group JDS-Uniphase (2001-2002) and finally with Stec Inc. of Japanese Horiba Group (2002-2003). Recently, activity of dielectric deposition group was dedicated to in-situ process control studies in continuous collaboration with Jobin-Yvon Horiba Group and in-depth research of HDP-PECVD mechanisms including modeling activities and development of new distributed plasma source for High Density ECR-PECVD.
Figure 4. MDECR-PECVD deposition chamber equipped with Jobin-Yvon Horiba UVISEL in-situ spectroscopic ellipsometer
For information on internships, doctoral studies, post-doctoral positions, or collaborations, please contact Dr. Pavel Bulkin