RF power dependence of the properties of n-type nanocrystalline silicon films deposited by a low-frequency inductively coupled plasma

• Published in: Journal of physics. D, Applied physics Applied physics, 2011-11, Vol.44 (45), p.455304-1-6
• Main Authors: Yan, W S, Xu, S, Sern, C C, Ong, T M, Zhou, H P
• Format: Article
• Language: English
• Subjects: Carrier density; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Debye length; Deposition; Electric power generation; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronic transport in multilayers, nanoscale materials and structures; Exact sciences and technology; Inductively coupled plasma; Materials science; Nanocrystalline materials; Nanocrystals; Nanocrystals and nanoparticles; Nanoscale materials and structures: fabrication and characterization; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures; Physics; Radio frequencies; Silicon films
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/0022-3727/44/45/455304

Nanocrystalline n-type silicon films are deposited by a low-frequency inductively coupled plasma at a low H 2 dilution, low working pressure of 2.0 Pa and low substrate temperature of 150 °C. The radio frequency (RF) power is set in the range 1000–1800 W. The RF power dependence of the structural, optical and electrical properties of the films is systematically studied. The x-ray diffraction patterns of the films present a (1 1 1)-preferred orientation when the RF power is increased from 1000 to 1800 W. The crystalline volume fraction of the films changes from 51% to 82% while the deposition rate of the films increases from 21 to 36 nm min −1 . The UV–VIS spectra show that the optical band gap is in the range 1.4–1.6 eV. Two characteristic hydrogen-related modes located at ∼630 and ∼2100 cm −1 are observed. The carrier concentration of the films ranges from 0.9 × 10 19 to 1.1 × 10 20  cm −3 depending on the applied RF power. When the RF power is increased, the electron density is increased and the Debye length is decreased while the electron temperature remains nearly constant. The doping mechanism of the present n-type nanocrystalline silicon films is revealed.