The Undoped Polycrystalline Diamond Film—Electrical Transport Properties

Abstract

The polycrystalline diamonds were synthesized on n-type single crystalline Si wafer by Hot Filament CVD method. The structural properties of the obtained diamond films were checked by X-ray diffraction and Raman spectroscopy. The conductivity of n-Si/p-diamond, sandwiched between two electrodes, was measured in the temperature range of 90–300 K in a closed cycle cryostat under vacuum. In the temperature range of (200–300 K), the experimental data of the conductivity were used to obtain the activation energies Ea which comes out to be in the range of 60–228 meV. In the low temperature region i.e., below 200 K, the conductivity increases very slowly with temperature, which indicates that the conduction occurs via Mott variable range hopping in the localized states near Fermi level. The densities of localized states in diamond films were calculated using Mott’s model and were found to be in the range of 9×1013 to 5×1014eV−1cm−3 depending on the diamond’s surface hydrogenation level. The Mott’s model allowed estimating primal parameters like average hopping range and hopping energy. It has been shown that the surface hydrogenation may play a crucial role in tuning transport properties.

Charge Transport Mechanisms of Black Diamond at Cryogenic Temperatures

“…Conversely, in the second activation energy temperature range, the pre-exponential factor related to the density of defective states in the 2T-8020 sample is about 50% higher than the one found for the 2T-9010, making this sample the more conductive at RT. The low value of the estimated activation energy for the electrical conduction is in agreement with previous reports of polycrystalline CVD diamond films [30,31], assuming Mott Variable Range Hopping (VRH) mechanism charge transport with activation energies ranging from 15.6 meV to 228 meV. This range of values depended on the film-growth procedure and then on the density of crystalline defects in the diamond thin film.…”

“…As already introduced in the paper, in defective polycrystalline CVD diamond thin films, the electrical transport has been modeled by the Mott's VRH [31]. According to this model, the variation of the conductivity with the temperature can be described by the expression:…”

The Barrier’s Heights and Its Inhomogeneities on Diamond Silicon Interfaces

“…The electrical contacts were formed by depositing gold dots of 5 mm in diameter by thermal evaporation on the diamond surface and back of the Si substrate. More details can be found in our earlier paper [ 6 ].…”

“…We believe that the electrical conductivity of diamond layers will depend on a graphite-like admixture located mainly on the surface of microcrystallites and therefore on the size of the microcrystallites themselves. Additionally, the diamond layers obtained by CVD methods are generally highly hydrogenated, which also has a large impact on their electrical conductivity as well [ 6 , 7 , 8 ]. It is now well established that a hydrogen-terminated diamond surface exhibits p-type conduction in a subsurface layer without doping [ 8 ], with carrier density around 10 10 –10 13 cm –2 [ 9 ].…”

Electrochemical Synthesis of Reduced Graphene Oxide/Gold Nanoparticles in a Single Step for Carbaryl Detection in Water

“…Fullerenes and carbon nanotubes have attracted considerable attention, especially CNTs, which are widely applied in sensing applications due to their electrochemical properties and their unusual structures [ 19 , 20 ]. Diamond films have significant potential in electrochemical application due to their resistance and stability [ 21 ]. Carbon allotropes include graphene, a 2D, thin-layer structure which is the basic building block of carbon allotropes, and nanomaterials containing oxygenated, hydrophilic functional groups [ 22 ].…”