"Surface Transfer Doping of Diamond and Ultrananocrystalline Diamond"

Speaker:Mr. Moshe Tordjman
Time:12:30 - 13:30
Remark:Ph.D Studnet of Prof. Rafi Kalish and Dr. Cecile Saguy
Abstract:Doping of diamond has drawn much attention in the last decades. When achieved, n- and ptype diamonds can
serve as superior building blocks for electronic devices benefiting of
diamond's extreme physical properties. Beside bulk doping of diamond, which has shown low
efficiency in term of activation energy, a new surface doping concept has been developed in the
last 10 years - the 'Surface Transfer Doping'.
Surface transfer doping takes advantage of a negative electron affinity of the diamond
surface when hydrogen terminated. Furthermore, when exposed to humid air, a high surface ptype conductive layer
(a few nanometers thick) isformed thanks to the transfer of electron
carriers from diamond valence band maximum to molecules' lower electrochemical potential.
Thin layers of Ultra Nano Crystalline Diamond (UNCD), composed of nano-sized
diamond crystallites (5-15nm) embedded in amorphous carbon (ta-C) were recently grown by
CVD methods. These exhibit many of the superior properties of diamond.
In our research, we have studies two aspects of diamond surface transfer doping:
1. The surface transfer doping effects of UNCD. This complex, combined with surface
transfer doping treatments, has striking electron field emission phenomenon in which a
switch-on and a reversible hysteresis ofthe emitted current occurs. These new
phenomena have been explained by us to be due to a double-barrier resonant-tunneling
of electrons through the quantumwells composed by a ta-C/Nano
Diamond/Adsorbent/Vacuum heterostructure.
2. The use of a new transfer doping material, Molybdenum Trioxide (MoO3), as a transfer
doping acceptor of H-terminated diamond replacing existing non-stable H2O molecules.
We show that MoO3has superior surface transfer doping properties - as far as electrical
conductivity and thermal stability are concerned.