Low temperature surface conductivity of hydrogenated diamond

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 104 to 105 Ω/□. We introduce a transport model where a disorder induced tail of localized states traps holes at very low temperatures (T 70 K) the hole density is approximately constant and the hole mobility μ is increasing two orders of magnitude. In the regime 70 K 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