Glueballs, Hybrids, Multiquarks. Experimental facts versus QCD inspired concepts

Hard amorphous (diamond-like) carbons

A model for the plasma enhanced chemical vapor deposition of amorphous hydrogenated silicon (a‐Si:H) in rf and dc discharges is presented. The model deals primarily with the plasma chemistry of discharges sustained in gas mixtures containing silane (SiH4). The plasma chemistry model uses as input the electron impact rate coefficients generated in a separate simulation for the electron kinetics and therefore makes no a priori assumptions as to the manner of power deposition. Radical densities and contributions to film growth are discussed as a function of gas mixture, electrode separation, and locale of power deposition, and comparisons are made to experiment. A compendium of reactions and rate constants for silane neutral and ion chemistry is also presented.

A model for the discharge kinetics and plasma chemistry during plasma enhanced chemical vapor deposition of amorphous silicon

This paper presents a critical review of the basic data concerning the physics and chemistry of low pressure SiH 4 glow discharges used to deposit hydrogenated amorphous silicon films (a-Si:H). Starting with an updated table of thermochemical data, we analyze the gas-phase elementary processes consisting of i) electron-molecule collisions, ii) ion-molecule collisions, iii) neutral-neutral collisions, iv) other electron and ion collisions involving electron-ion and ion-ion recombination, electron attachment on radicals and detachment of anions, and v) cluster growth kinetics in dusty plasmas. Experimental data or theoretical estimates are given and discussed in terms of cross-sections. collision and reaction rate constants, and transport coefficients. We also analyze the surface processes and reaction probabilities of ions, radicals and molecules.

Cross-Sections, Rate Constants and Transport Coefficients in Silane Plasma Chemistry

Nonthermal plasmas have emerged as a viable synthesis technique for nanocrystal materials. Inherently solvent and ligand-free, nonthermal plasmas offer the ability to synthesize high purity nanocrystals of materials that require high synthesis temperatures. The nonequilibrium environment in nonthermal plasmas has a number of attractive attributes: energetic surface reactions selectively heat the nanoparticles to temperatures that can strongly exceed the gas temperature; charging of nanoparticles through plasma electrons reduces or eliminates nanoparticle agglomeration; and the large difference between the chemical potentials of the gaseous growth species and the species bound to the nanoparticle surfaces facilitates nanocrystal doping. This paper reviews the state of the art in nonthermal plasma synthesis of nanocrystals. It discusses the fundamentals of nanocrystal formation in plasmas, reviews practical implementations of plasma reactors, surveys the materials that have been produced with nonthermal pla...

Nonthermal Plasma Synthesis of Nanocrystals: Fundamental Principles, Materials, and Applications

We present a study on the development and the evaluation of a fully automated radio‐frequency glow discharge system devoted to the deposition of amorphous thin film semiconductors and insulators. The following aspects were carefully addressed in the design of the reactor: (1) cross contamination by dopants and unstable gases, (2) capability of a fully automated operation, (3) precise control of the discharge parameters, particularly the substrate temperature, and (4) high chemical purity. The new reactor, named ARCAM, is a multiplasma‐monochamber system consisting of three separated plasma chambers located inside the same isothermal vacuum vessel. Thus, the system benefits from the advantages of multichamber systems but keeps the simplicity and low cost of monochamber systems. The evaluation of the reactor performances showed that the oven‐like structure combined with a differential dynamic pumping provides a high chemical purity in the deposition chamber. Moreover, the studies of the effects associated with the plasma recycling of material from the walls and of the thermal decomposition of diborane showed that the multiplasma‐monochamber design is efficient for the production of abrupt interfaces in hydrogenated amorphous silicon (a‐Si:H) based devices. Also, special attention was paid to the optimization of plasma conditions for the deposition of low density of states a‐Si:H. Hence, we also present the results concerning the effects of the geometry, the substrate temperature, the radio frequency power and the silane pressure on the properties of the a‐Si:H films. In particular, we found that a low density of states a‐Si:H can be deposited at a wide range of substrate temperatures (100 °C≤Ts≤300 °C).

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A fully automated hot-wall multiplasma-monochamber reactor for thin film deposition

Dissociation cross sections of silane and disilane by electron impact

The growth process, optical and structural properties of a‐Si:H films deposited from a silane multipole dc discharge are analyzed by real time and spectroscopic ellipsometry, and ir absorption spectroscopy. Films deposited mainly from neutral polymerized species are systematically compared to films deposited from monomeric ionic species at various ion incident energy up to 100‐eV. An increase of ion bombardment energy is shown to favor the formation of high density homogeneous and isotropic films.

Growth of hydrogenated amorphous silicon due to controlled ion bombardment from a pure silane plasma

A silane plasma is generated by a hot cathode dc discharge in a partially confining multipolar magnetic structure yielding hydrogenated amorphous silicon thin films on the walls. The low‐pressure range (0.1–5 mTorr) allows the analysis of the elementary processes for SiH4 dissociation. At low silane partial pressure the deposition rate remains in the range of 1–10 A/sec, but the contribution of ions to deposition can reach up to 80% in contrast with standard glow discharges.

Silane dissociation mechanisms and thin film formation in a low pressure multipole dc discharge

A dual-plasma [surface wave-coupled microwave (MW) at 2.45 GHz and capacitively coupled radio frequency (rf) at 13.56 MHz] reactor called MORFAX was developed for the deposition of amorphous wide band-gap alloys (a-SiOx:H, a-SiNy:H) at high growth rates and at low temperatures compatible with usual polymer substrates. These optical thin films may be used as components of multilayer coatings, such as index gradient devices or transparent interferential filters, to protect optical polymers. The dual-plasma MORFAX reactor was designed to provide three advantages: a high reactive species density (MW), a chemical selectivity due to the separation of the MW plasma and the rf plasma regions, and a variable ion bombardment energy due to the rf plasma dc polarization. Using O2, NH3, or N2 gases diluted in He–Ar mixtures in the microwave plasma while silane was injected in the postdischarge region, we have obtained the following information. (i) Optical emission spectroscopy shows the changes in the electron energy...

J. Huc

Papers

A fully automated hot-wall multiplasma-monochamber reactor for thin film deposition

Dissociation cross sections of silane and disilane by electron impact

Growth of hydrogenated amorphous silicon due to controlled ion bombardment from a pure silane plasma

Silane dissociation mechanisms and thin film formation in a low pressure multipole dc discharge

Dual-plasma reactor for low temperature deposition of wide band-gap silicon alloys