2013

Laser-Induced Incandescence of Microparticles Deposited on Surfaces ofTransparent Materials[1] Organization
Project Leader: Serge Zelensky, D.Sc., Prof.
(Taras Shevchenko National University ofKyiv, Ukraine).
Representative at RIE: Toru Aoki, Ph.D., Prof.
(Research Institute of Electronics, Shizuoka
University, Japan).
Participants:
Kateryna Zelenska, Ph.D., Engineer (TarasShevchenko National University of Kyiv,Ukraine)
Maksym Kokhan, MSc student (TarasShevchenko National University of Kyiv,
Ukraine).
[2] Progress of Scientific Activity
According to the research plan of the project,
the following scientific activities wereperformed at Taras Shevchenko National
University of Kyiv and at Research Institute ofElectronics, Shizuoka University:i.
computer simulations,ii.
development of a suitable method ofdeposition of carbon microparticles ona flat surface, andiii.
measurementsoflaser-induced
incandescence (LII) of the particles
deposited according to the method (ii).
The mentioned activities were performed atTaras Shevchenko National University of Kyiv,
Faculty of Physics, Department of Optics (i–iii)
and Research Institute of Electronics, Shizuoka
University (ii–iii).
The computer simulations were intended toestimate the effect of the surface material
parameters on the characteristics of LII of a
microparticle located on the surface of atransparent material.
For the particles deposition and LII
measurements, two YAG:Nd pulsed lasers withdifferent characteristics were used at TSNUK
and at RIE. For characterization of the surfaces
with deposited particles, an atomic force
microscope and a scanning electron microscopewere used at TSNUK and at RIE.
Besides the above-mentioned, the activities
included discussions of the project course andof the obtained results. During the period of theproject, the participants discuss its progress via
e-mail and on meetings in Kyiv, August andSeptember 2017, when Prof. Toru Aoki visitedUkraine.
The participants of the project actively
collaborated in organizing the 18th Intern.
Young Scientists Conference “Optics & HighTechnology Material Science” SPO 2017 heldat the Faculty of Physics of Taras Shevchenko
National University of Kyiv 26-29 Oct. 2017.
Prof. S. Zelensky was the member of theProgram Committee, Prof. T. Aoki was themember of the International Committee, and Dr.
K. Zelenska and Prof. T. Aoki were themembers of the Organizing Committee of SPO2017. Prof. S. Zelensky presented the projectrelated results at SPO-2017 and XXIII ISSSMC
conferences.
[3] Research Results
The project was aimed to investigate theproperties of LII of microparticles located on aflat surface of a transparent material. As a
primary task, the project scheduled theinvestigation of the effect of the surface thermal
conductivity on LII kinetics. The main idea isthat the surface’s thermal conductivity cansignificantly affect the decay of LII, hence LII
can be a promising method for visualization oflocal thermal properties of surface layers (atleast for transparent materials).
For the mentioned purpose of the project,carbon microparticles are the best candidate formeasurements. Carbon particles are easy to bedeposited on a surface by laser ablation; carbon
has high absorption coefficient at thewavelength of YAG:Nd laser and hightemperature of vaporization (approximately
4000K at atmospheric pressure).
Prior to the measurements of LII of surfacedeposited microparticles, computer simulations
were performed. In the calculations, a single
light-absorbing particle located on a flat surfaceof transparent material was irradiated by asingle laser pulse. Due to the absorption of laser
radiation, the particle can be heated toheat capacity, ρ is the density, α is theabsorption coefficient, F. is the laser power
density (the Gaussian-shaped laser pulse withthe length of 20 ns was used). The absorption oflaser radiation was accounted with thefollowing equation(2)dF = −αF dz ,where the coordinate z presents the direction of
the laser beam propagation.
For simplification of the calculations, theparticle shape was chosen as shown in Fig.1. In
the figure, irradiated is the top surface with thearea of π ( D 2 ) , and the size of the particle-tosurface contact spot (diameter d) is a variableparameter.

the current project, the efforts wereconcentrated on the characteristics of LII decay,
because the decay time measurements do not
require strict stabilization of laser parameters,
whereas the LII intensity is extremely sensitive
to the fluctuations of laser power density.
Temperature at (0,0)

incandescenttemperatures.
Transienttemperature field T(r,t) can be calculated withthe use of classical equation of thermal
diffusion∂T,(1)
div ( κ gradT ) + aF = rc p∂twhere κ is the thermal conductivity, c p is the4000
3000
2000
1000
00100200t, ns300

Fig.2. Calculated particle temperature history.
Coordinates (0,0) correspond to the center ofthe particle’s top surface.

2DzdH

As an example, Fig.3 presents the calculated
LII oscillograms for carbon particles on twosurfaces with different thermal diffusion
characteristics. As is seen from the figure, LII
decay time for sapphire surface is twice assmall as for glass surface, and this difference iscaused by the differences in thermal
conductivity and heat capacity of sapphire andglass.
2.0

The oscillograms of thermal emission at a
fixed wavelength were calculated with Planck’s
blackbody emission law with the use oftransient temperature field T(r,t) calculated withequations (1) and (2).
Typical calculated oscillograms of LII of acarbon particle located on a glass surface are
given in Fig.2 and 3, where the particle
dimensions are the following: D = H = 1 µm, d= D/10. In the calculations, LII signal iscollected from the top and side surfaces of theparticle, at a fixed wavelength of 450 nm.
Computer modeling was performed forsurface materials with different thermaltransport characteristics. The calculations showthat thermal conductivity of the surface material
affects (i) the intensity of LII, and (ii) the timeof LII decay. With the increase of the surface
thermal conductivity, the intensity of LII
decreases, and the LII decay time shortens. Inτglass ~ 40 ns

1.5ILII, a.u.

Fig.1. Carbon particle dimensions (D –diameter, H – height, d – particle-to-surface
contact spot diameter).

τsapphire ~ 20 ns

1.0glass
sapphire

0.50.0050

100 150
τ, ns

200

250

Fig.3. Calculated LII oscillograms for a carbon
particle on a glass surface and on a sapphiresurface.
Thus the above-given results of computer
simulations show that LII decay time of
surface-located carbon particles can be used forsensing the thermal characteristics of thesurface’s material.
For experimental verification of thementioned conclusion, measurements wereperformed with carbon miroparticles depositedon different surfaces by laser ablation technique.
Laser deposition was made in the air with the100ILII, a.u.

80
60

100Sapphire
Glass

80

τLII, nsuse of different carbon sources: china ink (driedon a glass surface), bulk carbon electrode rod,carbon-containing light-tight paper, carbon
black powder. Size of the deposited particles
was measured by scanning electron microscopy
and by atom force microscopy methods. The
size of the laser-deposited particles wasapproximately (0.2–0.5) µm.
Typical oscillograms of LII of surfacedeposited carbon microparticles are given in
Fig.4. Numbers near the curves represent thenumbers of laser shots in the sequence.

60402000510N
Fig.5. LII decay time as a function of the laser
shot number in the sequence for carbon
particles on glass and sapphire surfaces.

40250

Thus we can conclude that the results ofcalculations and the experimental data confirm
the main idea of the project: the LII decay timeof carbon-on-surface samples depend on thesurface material’s thermal properties.

Fig.4. Typical LII oscillograms of carbon
microparticles deposited on a glass surface bylaser ablation technique.

[4] Publications (published and submitted by
the CRP participants during the project
period 2017/5/24 – 2018/3/31)

2012
50-20-50050

100

150200t, ns

The LII oscillograms in Fig.4 were collectedwith the use of a photomultiplier (with timeresolution of 1.3 ns) and a digital oscilloscope(with the bandwidth of 200 MHz). Spectralinterval of LII was approximately (400–450) nm.
For better visual demonstration of the laserinduced changes of LII decay time, theoscillograms in Fig.4 are normalized by theirmaximal values.
As is seen from Fig.4, with the increase of
the laser irradiation dose N, the oscillograms
become shorter. This fact can be interpreted asa consequence of decrease of size of theparticles due to the laser-induced vaporization.
The effect of laser-induced vaporization can bereduced by the decrease of laser intensity in theexperiments.
Fig.5 presents the LII decay time as afunction of the number of laser shots in thesequence, for two surfaces of different
transparent materials: glass and sapphire. Bothof the surfaces were polished.
As is seen from Fig.5, at N>5, the LII decay
timeofcarbon-on-glass
sampleisapproximately twice as large as of carbon-onsapphire sample. This result is in agreementwith the results of calculations given in Fig.3.

1. K. Zelenska, S. Zelensky, A. Kopyshinsky Effectof Thermal Conductivity of Carbon Superficial
Layers on the Kinetics of Laser-Induced
Incandescence// Thai J. Nanosci. Nanotechnol.
2017. V.2. N.1. P.1–8.
2. V. Karpovych, K. Zelenska, S. Zelensky, S. Yablochkov, T. Aoki Evolution of Laser-Induced
Incandescence of Porous Carbon Materials underIrradiation by a Sequence of Laser Pulses// Thai J.
Nanosci. Nanotechnol. 2017. V.2. N.2.
3. M. Kokhan,
I. Koleshnia, S. Zelensky, Y. Hayakawa, T. Aoki
Laser-induced Incan-descence of GaSb/InGaSb
Surface Layers// XXIII Galyna Puchkovska
Intern. School-Seminar “Spectroscopy ofMolecules and Crystals”. Kyiv, Ukraine, Sept.
20–25, 2017. P.197.
4. V. Karpovych,
S. Zelensky,
S. Yablochkov
Laser-induced incandescence of porous carbon
materials under pulsed laser irradiation/ “Optics& High Technology Material Science” SPO 2017.
Scientific works. Oct. 26–29, 2017. Kyiv,
Ukraine. P.121.
5. M. Kokhan,
I. Koleshnia,
S. Zelensky,
Y. Hayakawa,T. AokiLaser-induced
Incandescence of GaSb/InGaSb Surface Layers//
Article under consideration in “Optics & Laser
Technology” journal.

Traveling Report
Name:

Serge Zelensky

Affiliation and address:

Taras Shevchenko National University of Kyiv,
60 Volodymyrska Street, Kyiv, 01033, Ukraine

Period of time:

10 November 2017 – 26 November 2017

Destination:

Research Institute of Electronics, Shizuoka UniversityPurpose:

Study of laser-induced incandescence and laser ablation of carbon withthe use of YAG:Nd laser and SEM measurements of laser-ablated carbon
microparticles for testing of the predictions of computer simulations.
Participation in scientific meetings at Research Institute of Electronics,
Shizuoka University during the period of stay.

Name of receiver:Prof. Toru Aoki