OPTICAL ACTIVE DIAGNOSTICS OF THERMAL AND ELECTRONIC PROPERTIES 
OF DIAMOND OF DIFFERENT STRUCTURES 
 
E. Ivakina, I. Kisialioua, P. Ščajevb, V. Gudelisb, K. Jarašiūnasb 
aInstitute of Physics, Academy of Sciences of Belarus, 220072 Minsk, Belarus 
bInstitute of Applied Research, Vilnius University, LT 10222, Vilnius, Lithuania 
 
Diamond is fairly recognized as a material of 21 century due to unchallenged combination 
of physical parameters, chemical and radiation resistance, biological inertness and so on.  
Unprecedented development of CVD – technology has increased  essentially an interest to the  
material, especially in view of promising potentials of diamond application in microelectronics, 
optoelectronics, sensors, optics and laser physics .  
 The problems of optical diagnostics and physical interpretation of thermal and 
electronic parameters of CVD-diamond as being a parameters of significance from point of view of 
practical application are solved in this project. Two teams of scientists from the  Institute of Applied 
Research (Vilnius) and Institute of Physics, Academy of Sciences (Minsk)  are involved in the 
project.  New effective methods of measurement and special scientific equipment based on up-to-
date lasers and detectors of optical signals have been developed. The measuring techniques are of 
contactless nature, provide  high temporal resolution and are currently realized in system 
OPTOPICOTEST (Minsk) and module HOLO-3 (Vilnius) . 
 The current project is a consequence and further evaluation of early implemented 
joint investigations in the same field via two-sided scientific and technical cooperation in 2002-
2005, as well as through the grant CBP.EAP.EV 982483 (2007 г.) in the framework of NATO 
program of scientific and technical cooperation. 
 Investigations currently conducted are aimed to  clarify physical factors  that affect 
the free charge carrier (FCC) dynamics as well as the processes of heat transfer  in CVD 
(polycrystals) and HPHT (synthetic monocrystals) diamonds of different structure and impurities 
content.. Two-photon absorption in diamond at 351 nm is proposed for FCC excitation. It enabled 
to carry out the volumetric excitation of samples and to measure the recombination time and 
diffusion coefficient within wide intervals of FCC density (1015 - 31017 cm-3) and sample 
temperature  (80-800К).  
0 1 2 3 4
10-2
10-1
 3.0x1017 cm-3
 9.9x1016 cm-3
 4.2x1016 cm-3
 1.1x1016 cm-3
=0.76 ns
=2.5 ns
=6.4 ns
 
ln
(T
0/T
)
Optical Delay (ns)
800 K
=23 ns(a)
 
                      Fig. 1 
100 1000
102
103
104  1 .5x10 15
 3 .5x10 15
 7 .5x10 15
 2 .3x10 16
 1x10 18
 ex=213  nm
slope = -2.8
 a 
(c
m
2 /V
s)
T  (K )
 ex=351 nm
(b)
 
                          Fig.2 
Besides, the FCC lifetime was controlled via induced absorption caused by FCC generation. 
A set of transmittance kinetics for HPHT diamond of IIa type at different pumping  levels is shown 
in Fig.1. Probing at 1053 nm, sample temperature  Т=800К.  The initial FCC density and lifetime 
are  given by the figures. The temperature dependence of ambipolar mobility  of FCC, as deduced 
from transient gratings excitation experiments are given in Fig.2.  
Thermal investigations of diamond samples was conducted by the method of transient 
gratings as well. Nevertheless in contrast to studies mentioned above, thermal gratings were probed 
with beam from CW He-Ne laser (wavelength 632 nm) because lifetime of thermal gratings was 
typically larger. The temporal behavior of the diffracted signal for CVD-diamond under excitation 
at 213 nm one can see in Fig.3. The two component of kinetics are well defined. The first pike 
downward – is electronic component  whereas slow part  – the thermal grating decay which is 
recorded due to non-radiative recombination of FCC. Electronic component has been studied by the 
equipment of high temporal resolution as it is described above. As it seen in Fig.3,  thermal 
component has the light induced refractive index of opposite sigh with respect to electronic one. It 
enables the in-plane thermal diffusivity measurement.  
0,6 0,8 1,0 1,2 1,4 1,6
-0,1
0,0
In
te
ns
ity
 o
f d
iff
ra
ct
io
n,
 a.
u
T ime,  s
scattered light level
 
0,5 1,0 1,5 2,0 2,5
0,01
2
1
In
te
ns
ity
 o
f d
iff
ra
ct
io
n,
 a
.u
.
Time, s
 
                                Fig.3                                                             Fig.4  
 
 The columnar- conical internal structure of crystallites in CVD-diamond was 
confirmed by the depth resolved thermal diffusivity measurement. The crystallites are oriented 
along normal to sample surface. Two kinetics one can see in Fig.4 that are obtained under diamond 
slab excitation at 213 nm with grating recording on growth (1) and nucleation (2) sides. As it shown 
by analysis conducted, thermal diffusivity of diamond may be several time larger for growth side as 
compared to nucleation side. The reason for this is that the crossection size of crystallite near 
nucleation side is typically less than that near the growth side.   
 The results obtained by conducted studies provide new data on CVD-diamond in 
comparison with monocrystalline samples. It gives the possibility to estimate the prospects of the 
material application in electronics and optoelectronics especially as hard radiation detectors and 
effective heat spreaders. Besides, the data obtained may be used for growth technologies  
development to produce the material of desired parameters.