Low Temperature Surface Conductivity of Hydrogenated Diamond

Abstract

Conductivity and Hall experiments are performed on hydrogenated poly-CVD, atomically flat homoepitaxially grown Ib and natural type IIa diamond layers in the regime 0.34 to 400 K. For all experiments hole transport is detected with sheet resistivities at room temperature in the range 10 4 to 10 5 W/ & . We introduce a transport model where a disorder induced tail of localized states traps holes at very low temperatures (T < 70 K). The characteristic energy of the tail is in the range of 6 meV. Towards higher temperatures (T > 70 K) the hole density is approximately constant and the hole mobility m is increasing two orders of magnitude. In the regime 70 K < T < 200 K, m is exponentially activated with 22 meV, above it follows a $T 3/2 law. The activation energy of the hole density at T < 70 K is governed by the energy gap between holes trapped in the tail and the mobility edge which they can propagate. In the temperature regime T < 25 K an increasing hole mobility is detected which is attributed to transport in delocalized states at the surface.

An insight of p-type to n-type conductivity conversion in oxygen ion-implanted ultrananocrystalline diamond films by impedance spectroscopy

“…3．The activation energy values for these samples are 0.10 eV, 0.11 eV, 0.04 eV and 0.11 eV, respectively. The activation energy of H-terminated surface conductivity is 3-20 meV in single and polycrystalline diamond films, 47 which is much lower than those of as-deposited sample and sample O12650. Ohmagariet et al 48 reported an activation energy of about 0.1 eV in B-doped p-type conductive UNCD films, in which conduction mechanism remains unknown.…”

Homoepitaxial diamond growth for the control of surface conductive carrier transport properties

“…The reason for this has been documented in detail elsewhere. 13,18 Briefly, the results obtained here can be explained by considering the dipole formed by the differing electronegativities of the carbon and hydrogen atoms at the hydrogen terminated surface. 5 This dipole can be considered to be responsible for both the origin of hydrogen surface conductivity and the mechanism of the carrier transport that is observed.…”

“…3,4 High performance devices have been fabricated utilizing this surface conductive layer; [5][6][7][8][9] however its origin is still under debate. [10][11][12][13] As it is not a dopant in the conventional sense, control over the carrier transport values to date has been elusive. Moderate success has been achieved by moderate annealing treatments in air to partially oxidize the surface, but this also increases the sheet resistivity which is obviously undesirable for device applications.…”

Hydrogenated Black Diamond: An Electrical Study

“…Figure 3 shows four point sheet resistivity measurements for samples A-D over the 10-300 K temperature range. The resistivity of all samples increases with decreasing temperature as is to be expected, the room temperature values being comparable with those available in the literature [3][4][5]15]. Figures 4 and 5 show the sheet carrier concentrations and carrier mobilities derived from the Hall measurements for samples A-D, plotted as a function of sample temperature.…”

“…Problems with doping diamond both n-type and p-type, due to the high density of the diamond lattice, have hindered the commercial realisation of devices. However, exposing diamond to a hydrogen plasma yields a surface conductive layer with p-type carriers of low activation energy [1][2][3][4][5][6][7][8][9]. This phenomenon has been utilised to fabricate diodes and field effect transistors on homoepitaxial and polycrystalline films, which display excellent characteristics at room temperature [10][11][12].…”