Structural and electronic properties of electron cyclotron resonance plasma deposited hydrogenated amorphous carbon and carbon nitride films

Abstract

Hydrogenated amorphous carbon and carbon nitride films (a-C1−xNx:H) have been synthesized from methane, acetylene, or acetylene–nitrogen precursor gases using a high density electron cyclotron resonance plasma. The deposition and etching rates, along with the film stoichiometry, density, Raman signature of the sp2 phase, and optical and transport properties, have been studied as a function of plasma parameters (microwave power and negative bias of the substrate). While low-density H-rich carbon films have been grown from methane for ion energies up to 200 eV, films grown using acetylene have been obtained at high deposition rate (1.1 nm s−1) with H content below 25 H at. % and density of 2.0 g cm−3, which makes them interesting as electronic materials. For dense carbon nitride alloys, the maximum (N/N+C)=0.35 is limited by the vanishing growth rate, which results from ion-assisted chemical etching mechanisms. A larger N2 plasma etching rate related with lower film density is observed for (N/N+C) values above 0.20. As a function of the N content, Raman spectra give evidence of a continuous structural ordering of the sp2 phase, which is confirmed by a modeling of the ohmic conductivity σ(T) data based on hopping transport within a bandtail distribution of localized π states. With increasing N content, a better overlap of p orbitals along with an increase in the localization length are expected as a consequence of a less constrained environment. A maximum of the room-temperature conductivity at (N/N+C)=0.28 reveals the onset of a transition towards polymeric alloys with lower mean coordination number.

Structural and Electronic Characterization of Nanocrystalline Diamondlike Carbon Thin Films

“…5 An important electronic property of such carbon based materials, which includes diamond, carbon nanotubes (CNT) and CNT-composites, is their ready ability to emit electrons into vacuum which make them suitable for applications in field emission display technology. 2,7,8 Diamond-like carbon (DLC) thin films are well known for their exceptional mechanical properties [9][10][11][12][13][14] and recently, we have explored the mechanical, optical and electrical properties of DLC and modified DLC thin films. [15][16][17][18][19] DLC thin films are known to emit electrons 20,21 , however, compared with diamond and CNTs, their threshold field (E T ) tends to be higher and emission current (I E ) is lower.…”

Principles for designing sputtering-based strategies for high-rate synthesis of dense and hard hydrogenated amorphous carbon thin films

“…For example, Godet et al [36] showed that polymeric a-C:H films exhibiting low mass densities (< 2 g/cm 3 ) and high H content (25%-40%) are grown under low RF bias powers using C2H2 as well as CH4 based ECR discharges while Baby et al [37] found a high average Raman base line slope at lower substrate bias potentials which corresponds to a high H content in the films when they deposited a-C:H films using C2H2/Ar based ICP discharge. In our case similar trends with respect to mass density are observed for films (see Fig.2) grown using HiPIMS+DCMS at Eion = -eVfl, whereas in 100% Ar HiPIMS case (where there is no intentional use of H) the film exhibit higher density at this ion energy values.…”

Photoconductivity and characterization of nitrogen incorporated hydrogenated amorphous carbon thin films

“…However, Ronning et al 13 have argued that nitrogen introduction increases the states, which changes the activation energy as well as conductivity. On the other hand, Godet et al 4,14 have suggested that nitrogen introduction causes a reduction of concentration of states and this governs the conduction mechanism.…”

“…Lazar et al 11 have developed a-C:H based metal-insulator-metal (MIM) and metal-insulator-semiconductor (MIS) structures and observed space charge limited conduction in their devices. While various other conduction mechanisms, which includes band tail hopping have also been reported [2][3][4] in films grown at low pressure, it remains important to understand the physics related to the conduction in a-C:H and modified a-C:H films especially those grown at high pressures.…”

“…Schwan et al 3 and Godet et al 4 have explored the electrical properties of a-C:H:N films and have suggested models which help to explain electron transport. Recently, we 5,6 have investigated some of the electrical properties of a-C:H:N and Ti/DLC multilayer films.…”