Atomic scale investigation of silicon nanowires and nanoclusters
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NANO REVIEW
Open Access
Atomic scale investigation of silicon nanowires and nanoclusters Manuel Roussel1*, Wanghua Chen1, Etienne Talbot1, Rodrigue Lardé1, Emmanuel Cadel1, Fabrice Gourbilleau2, Bruno Grandidier3, Didier Stiévenard3 and Philippe Pareige1
Abstract In this study, we have performed nanoscale characterization of Si-clusters and Si-nanowires with a laser-assisted tomographic atom probe. Intrinsic and p-type silicon nanowires (SiNWs) are elaborated by chemical vapor deposition method using gold as catalyst, silane as silicon precursor, and diborane as dopant reactant. The concentration and distribution of impurity (gold) and dopant (boron) in SiNW are investigated and discussed. Silicon nanoclusters are produced by thermal annealing of silicon-rich silicon oxide and silica multilayers. In this process, atom probe tomography (APT) provides accurate information on the silicon nanoparticles and the chemistry of the nanolayers. Introduction Low-dimensional nano-structured materials, such as carbon nanotubes [1], silicon nanowires (SiNWs) [2], and silicon nanoclusters (SiNCs) [3], have attracted much interest in recent years because of their special properties (electrical, optical, mechanical, etc.) compared to bulk materials. The morphology and number density of nanoclusters as well as the dopant or impurity concentration and their spatial distributions in nanowires can greatly affect their properties. Thus, a key issue that remains is to analyze and characterize nano-structured materials at the atomic scale. In this study, we have used the laser-assisted wide angle Tomographic Atom Probe to characterize SiNWs and SiNCs, respectively. The atom probe tomography (APT) involves the use of a three-dimensional (3D) high-resolution analytic microscope that can map the spatial distribution of atoms in materials at the atomic scale. The principle of the APT is based on the field evaporation of atoms. A conventional APT relies on the basic principle of the field evaporation of atoms from the surface of a specimen under high-voltage (HV) pulses [4,5]. The chemical nature of each evaporated ion is determined by the time of flight mass * Correspondence: [email protected] 1 Groupe de Physique des Matériaux, Université et INSA de Rouen, UMR CNRS 6634 - Av. de l’université, BP 12, 76801 Saint Etienne du Rouvray, France. Full list of author information is available at the end of the article
spectrometry using a position-sensitive detector (PSD). The set of information (position and chemical nature) allows for the 3 D reconstruction of the ionized volume. The specimen must be prepared in the form of a sharp needle with a diameter smaller than 100 nm to generate a sufficient electric field at the apex to favor the ionization and evaporation of atoms during HV pulses. In the case of poor conductive materials such as semiconductor NWs, HV pulses are replaced by femtosecond laser pulses to evaporate the semiconducting materials. This is the so called laser-assisted APT. The laser pulse frequency triggers the e
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