skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Quantum confinement effect in crystalline silicon quantum dots in silicon nitride grown using SiH{sub 4} and NH{sub 3}

Abstract

Crystalline silicon quantum dots (Si QDs) were spontaneously grown in the silicon nitride films by plasma-enhanced chemical vapor deposition using SiH{sub 4} and NH{sub 3} as precursors. When the size of the Si QDs was reduced from 4.9 to 2.9 nm, the photoluminescence peak energy was shifted from 1.73 to 2.77 eV. The photoluminescence peak energy was fitted to the relationship, E(eV)=1.13+13.9/d{sup 2}, where d is the diameter of the Si QD in nanometers. The measured band-gap energies of the Si QDs were in good agreement with the quantum confinement model for crystalline Si QDs. These results suggest that the hydrogen dissociated from NH{sub 3} plays an important role in improving the crystallinity and surface passivation of Si QDs.

Authors:
; ; ;  [1]
  1. Department of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of)
Publication Date:
OSTI Identifier:
20778857
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 88; Journal Issue: 12; Other Information: DOI: 10.1063/1.2187434; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; AMMONIA; CHEMICAL VAPOR DEPOSITION; CONFINEMENT; ENERGY GAP; HYDROGEN; PASSIVATION; PHOTOLUMINESCENCE; PLASMA; QUANTUM DOTS; SEMICONDUCTOR MATERIALS; SILANES; SILICON; SILICON NITRIDES; THIN FILMS

Citation Formats

Kim, Tae-Wook, Cho, Chang-Hee, Kim, Baek-Hyun, and Park, Seong-Ju. Quantum confinement effect in crystalline silicon quantum dots in silicon nitride grown using SiH{sub 4} and NH{sub 3}. United States: N. p., 2006. Web. doi:10.1063/1.2187434.
Kim, Tae-Wook, Cho, Chang-Hee, Kim, Baek-Hyun, & Park, Seong-Ju. Quantum confinement effect in crystalline silicon quantum dots in silicon nitride grown using SiH{sub 4} and NH{sub 3}. United States. doi:10.1063/1.2187434.
Kim, Tae-Wook, Cho, Chang-Hee, Kim, Baek-Hyun, and Park, Seong-Ju. Mon . "Quantum confinement effect in crystalline silicon quantum dots in silicon nitride grown using SiH{sub 4} and NH{sub 3}". United States. doi:10.1063/1.2187434.
@article{osti_20778857,
title = {Quantum confinement effect in crystalline silicon quantum dots in silicon nitride grown using SiH{sub 4} and NH{sub 3}},
author = {Kim, Tae-Wook and Cho, Chang-Hee and Kim, Baek-Hyun and Park, Seong-Ju},
abstractNote = {Crystalline silicon quantum dots (Si QDs) were spontaneously grown in the silicon nitride films by plasma-enhanced chemical vapor deposition using SiH{sub 4} and NH{sub 3} as precursors. When the size of the Si QDs was reduced from 4.9 to 2.9 nm, the photoluminescence peak energy was shifted from 1.73 to 2.77 eV. The photoluminescence peak energy was fitted to the relationship, E(eV)=1.13+13.9/d{sup 2}, where d is the diameter of the Si QD in nanometers. The measured band-gap energies of the Si QDs were in good agreement with the quantum confinement model for crystalline Si QDs. These results suggest that the hydrogen dissociated from NH{sub 3} plays an important role in improving the crystallinity and surface passivation of Si QDs.},
doi = {10.1063/1.2187434},
journal = {Applied Physics Letters},
number = 12,
volume = 88,
place = {United States},
year = {Mon Mar 20 00:00:00 EST 2006},
month = {Mon Mar 20 00:00:00 EST 2006}
}
  • The densities of N, NH, and NH{sub 2} radicals in a remote Ar-NH{sub 3}-SiH{sub 4} plasma used for high-rate silicon nitride deposition were investigated for different gas mixtures and plasma settings using cavity ringdown absorption spectroscopy and threshold ionization mass spectrometry. For typical deposition conditions, the N, NH, and NH{sub 2} radical densities are on the order of 10{sup 12} cm{sup -3} and the trends with NH{sub 3} flow, SiH{sub 4} flow, and plasma source current are reported. We present a feasible reaction pathway for the production and loss of the NH{sub x} radicals that is consistent with the experimentalmore » results. Furthermore, mass spectrometry revealed that the consumption of NH{sub 3} was typically 40%, while it was over 80% for SiH{sub 4}. On the basis of the measured N densities we deduced the recombination and sticking coefficient for N radicals on a silicon nitride film. Using this sticking coefficient and reported surface reaction probabilities of NH and NH{sub 2} radicals, we conclude that N and NH{sub 2} radicals are mainly responsible for the N incorporation in the silicon nitride film, while Si atoms are most likely brought to the surface in the form of SiH{sub x} radicals.« less
  • The reaction of ground-state silicon ion with silane is investigated by using a guided ion beam tandem mass spectrometer. Reaction cross sections of all possible fragments, Si/sub m/H/sub n//sup +/ (m = 1, 2; n = 0, 1, 2, 3), as a function of relative kinetic energy are determined. All thermal energies, the major product is Si/sub 2/H/sub 2//sup +/. One remarkable reaction, the interchange of the projectile silicon ion with the target silicon atom, is observed at near zero kinetic energy. Labeling experiments employing /sup 30/Si/sup +/ for the beam or SiD/sub 4/ for the reactant indicate the intermediacymore » of the disilicon hydrides for the formation of the observed products. From the endothermicities of several reactions, the 298 K heats of formation for several ionic and neutral silicon hydrides are derived: ..delta..H/sub f//sup 0/(SiH) = 90.0 +/- 1.7, ..delta..H/sub f//sup 0/(SiH/sub 2/) = 69.0 +/- 2, ..delta..H/sub f//sup 0/(SiH/sub 3/) = 48.5 +/- 1.6, ..delta..H/sub f//sup 0/(SiH/sub 2//sup +/) = 276.1 +/- 1.7, ..delta..H/sub f//sup 0/(SiH/sub 3//sup +/) = 237.1 +/- 2, ..delta..H/sub f//sup 0/(Si/sub 2//sup +/) less than or equal to 328.0 +/- 2, ..delta..H/sub f//sup 0/(Si/sub 2/H/sup +/) less than or equal to 304.4 +/- 1.6, ..delta..H/sub f//sup 0/(Si/sub 2/H/sub 2/) less than or equal to 268.0 +/- 2.6, ..delta..H/sub f//sup 0/(Si/sub 2/H/sub 3//sup +/) = 266 +/- 2, all in kcal/mol. From an evaluation of these and other experiments, values of ..delta..H/sub f//sup 0/(SiH/sub 2//sup +/) and ..delta..H/sub f//sup 0/(SiH/sub 2/) of 278.0 +/- 1.4 and 68.5 +/- 1.5 kcal/mol, respectively, are recommended.« less
  • Semiconductor fabrication often requires the deposition of hydrogenated silicon nitride (SiN{sub x}H{sub y}) film using SiH{sub 4}/NH{sub 3}/N{sub 2}/He capacitively coupled plasma (CCP) discharge. As analysis of the discharge geometry is essential to understanding CCP deposition, the effect of electrode spacing on the two-dimensional distributions of electrons, ions, and metastable and radical molecules was analyzed numerically using a fluid model. The simulation shows that the spatial variations in the ionization rates near the sheath become more obvious as the electrode spacing increases. In addition, as molecule-molecule gas-phase reactions are significantly affected by the local residence time, large electrode spacings aremore » associated with significant volumetric losses for positive ions. Consequently, an increase of the electrode spacing leads axial density profiles of ions to change from bell shaped to double humped. However, NH{sub 4}{sup +} persistently maintains a bell-shaped axial density profile regardless of the degree of electrode spacing. We set the mole fraction of NH{sub 3} to only 1% of the total flow at the inlet, but NH{sub 4}{sup +} is the most abundant positive ion at the large electrode spacings. As the gas flow can transport the radicals around the space between the electrodes, we found that radical density distribution shifts toward the grounded electrode. The shift becomes pronounced as the electrode spacing increases. Finally, to validate our model, we compared the calculated deposition rate profile with the experimental data obtained along the wafer radius. According to our numerical results, the SiN{sub x}H{sub y} deposition rate decreases by approximately 16% when the electrode spacing increases from 9 to 20 mm.« less
  • Brief 400-nm photolysis of 1:10 silane/argon matrices containing monatomically isolated aluminum results in the formation of the insertion product silylaluminum hydride (SiH{sub 3}AlH), most likely via an oxidative addition mechanism. The techniques of UV-vis, EPR, and infrared spectroscopy enabled the identification and characterization of this molecule. The photolytic generation of this species paralleled the formation of methylaluminum hydride (CH{sub 3}AlH) studied previously in the authors laboratory. EPR spectral simulations and ab initio self-consistent-field molecular orbital (SCF MO) calculations were employed to help in the characterization of silylaluminum hydride. The EPR spectral parameters extracted from the raw data via the computermore » simulations, along with subsequently calculated atomic orbital spin densities, determined that the molecule was a bent, orthorhombic species. The SCF MO calculated bond angle at the Al atom was shown to be 118.80{degree}. Secondary photolysis of the aluminum/silane matrix sample resulted in the conversion of the insertion product back to that of the ground-state complex most likely by a reductive elimination mechanism.« less
  • By using a high density microwave-induced plasma source, depositions of crystalline silicon films from SiH{sub 4}+He mixture are investigated systematically. Microwave power and SiH{sub 4} flow rate are used as the variable deposition parameters. Results demonstrate that film deposition rate increases with increasing both the microwave power and the SiH{sub 4} flow rate. While film crystallinity promotes with increasing the microwave power but degrades with increasing the SiH{sub 4} flow rate. After optimizing the film deposition conditions, highly crystallized Si films are deposited at a rate higher than 1000 nm/s. Promotion of the dissociation efficiency of source gases and enhancementmore » in the diffusion length of film precursors on growing surface are suggested to be main factors responsible for the simultaneous achievements of the high deposition rate and the high film crystallinity. Mechanisms under these phenomena are discussed in detail.« less