「様式３」Project No.： 2016

Modification of optical and electronic properties ofsurface layers and thin films by laser treatment［１］Organization（10.5 points）
Project Leader：
Leonid Poperenko, Dr., Professor,
Head of Optics chair (Faculty of Physics, Taras
Shevchenko National University of Kyiv,Ukraine)
Representative at RIE：
Toru Aoki, Ph.D., Prof. (ResearchInstitute of Electronics, Shizuoka University,Japan)
Participants：
Oleksandr Stronskyi, Dr., Professor,
Head of department “Physics of optoelectronicdevices” (V.E. Lashkaryov Institute ofSemiconductor Physics of the National
Academy of Sciences of Ukraine, Ukraine)
Iryna Yurgelevych, Ph.D., Senior
Scientist (Faculty of Physics, Taras Shevchenko
National University of Kyiv, Ukraine)
Dmytro Gnatyuk, Ph.D., JuniorReseacher (Faculty of Physics, Taras
Shevchenko National University of Kyiv,Ukraine)［２］Research Progress（10.5 points）
The project research was dedicated to theinfluence of laser treatment on optical andelectronic properties of silicon and amorphous
metallic alloys. Optical conductivity of thenanostructured silicon formed as isolated cellson the single crystal silicon wafers by methodof laser ablation and rapidly quenchedmulticomponent alloy ribbons as functions oflaser pulse energy as well as a number ofpulses was studied.
The participants of the project were involved inorganizing of the 19th Intern. Young Scientists
Conf. “Optics & High Technology MaterialScience” SPO 2018 which was held at theFaculty of Physics, Taras Shevchenko National
University of Kyiv, 25-28 October 2018.
Ph.D. D. Gnatyuk attended the 17thInternational Conference on Global Researchand Education, Inter-Academia 2018 (iA-2018)
in Kaunas, Lithuania, 24-27 September 2018.
［３］Results（10.5 points）(３－１) Research resultsNanostructured silicon was formed on thesurface of single-crystal silicon (100)orientation wafer with the natural oxide layer
by laser ablation. Irradiation was performed in
an air atmosphere. The nanostructured silicon
was formed by Yb-doped fiber laser which
generates pulses with energies up to 1 mJ at afrequency of 1 MHz with a wavelength of 1060
nm. The power of laser irradiation on thesurface of the monocrystalline silicon ranged
from 100 mW to 1 W. Scan modes of laser
beam provide a synthesis of nanostructured
particles of silicon dioxide or silicon
nanoparticles. On the surface of silicon wafer
the nanostructured layers in the form of
separate cells were created. Wave structure as
rowing along the short side of a rectangular cell
was formed on the surface of cells (Fig. 1).
Ribbon samples of (Fe0.9Cr0.1)85B15 alloys (12 nm
in width and 30-35 m in thickness) for thisstudy were prepared by rapidly-quenchedmethod. Laser treatment of the sample
surfaces was performed in air using a YAG
free-running pulse laser (wavelength =1.06 m,pulse duration 4 ms, and frequency 1 pulse persecond). The diameter of the incident beam
was equal to 14 mm. The pulse energy E andthe number of pulses N (“dose”) varied from 1
to 25 kJ/m2 and from 20 to 400, respectively.

Fig. 1. Optical microscopy image of therectangular cell of nanostructured silicon.
In order to provide uniform irradiation of thesurfaces, the samples, which were placed on abulk heat-removing substrate, were scanned bylaser beam which was normally incident to thesurface. The thermal effect T during the laser
treatment was measured at the untreated faceof the sample and did not exceed 50 K at themaximum irradiation dose.
Optical polarimetric measurements of siliconwafer and (Fe0.9Cr0.1)85B15 ribbons were carriedout using laser ellipsometer LEF-3M-1 at awavelength  = 632.8 nm. The angulardependences of the ellipsometric parameterssuch as a phase shift  between the orthogonalcomponents of the polarization vector and anazimuth  of the restored linear polarization
were obtained for the investigated samples. Allangulardependenciesofellipsometricparameters cos() and tg() of the samples
were analyzed and the principal angle p oflight incidence (cos=0) and tgp (the value tg
at p) were obtained. Optical polarimetricmeasurements were carried out within theseveral cells on the silicon wafer and areas
located between the cells for two mutuallyperpendicular directions (azimuthal angles  =90º and  = 0º respectively) in own plane of thesample. For estimation of electronic propertiesof the surface layers the optical conductivity for different areas of silicon sample surface arecalculated according to the semi-infinite
medium approximation.
n = sinptgpcos2p,
k = sinptgpsin2p, = nkc/,where n is a refractive index, k is an absorption
index and c is the light speed.
The obtained ellipsometric parameters p, tgp
and the calculated optical conductivity  fordifferent areas of the silicon sample surface,
namely areas which are located between two
neighboring cells (1) and placed within one of
the cells of the nanostructured silicon
specimen (2) are given in Table 1.
It is seen from the Table 1 that changes of theellipsometric parameters p and tgp for two
mutually perpendicular directions in own planeof the sample do not exceed the measurement
errors,namelyp = 0.01
andtgp = 0.0010 for area located between thecells of silicon wafer (1). For cell of thenanostructured silicon specimen (2) there are
significant differences in the values p and tgpfor two cell orientations ( = 90º and  = 0º)
relatively p-direction of the sample. For thecalculated optical conductivity similar changesare observed. In comparison to almost
unchanged data for area 1, the values of opticalconductivity within area 2 are changed in six
times relatively to each another for two
mutually perpendicular directions in own planeof the sample relatively its p-direction. Similar
results were obtained for other investigatednanostructured silicon cells.
Table 1. Ellipsometric parameters p, tgp and for two different areas of the silicon sample
surfacearea12

direction

p,ºtgp

, 1015 s-1

 = 90º = 0º = 90º = 0º75.4275.44
54.37
63.57

0.03840.03910.10320.4731

0.49
0.51
0.12
0.74

Moreover the angle dependencies of parametercos for one of the cells of silicon sample
measured at four angle positions of the wafer
in its own plane due to rotations by step of 45
degrees are presented in Fig. 2. It is seen that
optical properties of the diagnosted cell arealso significantly different for azimuthal
measurements of nanostructured siliconsample due to formed therein surface structure

after the action of the powerful laser.
So, optical properties for each cell formed on
the silicon surface after laser action are
anisotropic. This feature indicates a presenceof strain and an appearance of the elastic
stresses inside the silicon layer subsurface
within the sample areas subjected to laser
processing. Such stress distribution within theskin layer probed by polarized light affects theatomic and electronic structure of this layer aswell as variations in its optical response to thelight excitation which are clearly recorded byellipsometric diagnostics in two perpendicular
azimuthal directions as well as four  angle
orientations.

properties of the amorphous ribbons after theaction of laser radiation.

cm -1cos

90
45
0
-45

,

Fig. 2. Dependencies of cos() for one of thecells of the irradiated monocrystalline siliconsample at orientations
 = 90º, 45 º, 0 º and -45º.
Amorphous metallic alloys in their optical andelectronic
properties
arebetween
semiconductors and classical metals. For
comparison in Fig. 3 the reflectance spectra ofribbons of typical amorphous alloys Fe67Cr18B15,
Fe75Ti5B20 and Fe70Ni20(GeSiB)10 in the infrared
region of 50-450 cm-1 measured by using
Fourier spectrometer are shown.
It is seen that behavior of optical properties ofthese alloys is not Drude-like ones within theinfrared region. But it is well-known that for
metallic materials the spectral behavior in thisrange must be similar to R  1(Hugen-Rubens relation) as wave numberν  0.
Therefore, it was interesting due to specificatomic and electronic structure of suchmaterials to investigate the behavior of opticalFig. 3. Reflectance spectra of the ribbons ofamorphous alloys Fe67Cr18B15 (1), Fe75Ti5B20 (2)and Fe70Ni20(GeSiB)10 (3). The scale on the rightrefers to curve 3. Curve 1 is displaced up by11%.
In Fig. 4 the optical conductivity  of(Fe0.9Cr0.1)85B15 ribbons as a function of thenumber of laser pulses N at a constant pulse
energy E=25 kJ/m2 (a) and 7 kJ/m2 (b) ispresented.
At low irradiation doses,  clearly decreases (byapproximately 0.7·1015 s-1, that much more thanthe error  = 0.1·1015 s-1) and reaches its
minimum at N=50 and 200. However, a further
increase in the laser irradiation dose results in
an increase of . The curves  (E) at a constantvalues N=200 and 50 are similar (Fig. 5, a,b).
Consequently, the experimentally observed
behavior of the optical conductivity  isassumed to be related to the structure
relaxation and transformation within thesurface layers of ribbons subjected to laser
treatment. The obtained results may beinterpreted as follows. In as-rapidly quenchedalloys prepared by the spinning technique theformation of crystal-like clusters or grains ofcrystalline phase is more probable near the freeformed surfaces of ribbons in condition of air
atmosphere than one near the contact surface,since the latter provides higher cooling rates
due to direct contact during fabrication withthe cooled rapidly rotating copper disk.

4,7

4,6

4,6

4,5

4,5

4,4

-1

4,4-154,3

*10 , s-1-15

*10 , s

4,7

4,3
4,2
4,1

4,2
4,1

4,0

4,0

3,9

3,9

0

100

200

300

400

010E, kJ/m

N

4,64,54,54,4-1

4,64,4

4,3

-15

4,7

4,3

4,2

4,1

4,0

4,0

3,93,91002030

4,24,1030a)

4,7*10 , s-15

*10 , s-1a)

202200300

0400

10E, kJ/mNb)
Fig. 4. Optical conductivity of (Fe0.9Cr0.1)85B15
amorphous metallic ribbons as a function of anumber of pulses N at constant pulse energy
E=25 kJ/m2 (a) and 7 kJ/m2 (b).
It is known that the optical conductivity
spectrum of crystalline bcc iron has a wide
absorption band in the photon energy range Eof 2-2.6 eV. The photon energy of probing lightin this study was equal to 2 eV.
This means that the observed decrease of theoptical conductivity  at the operating
wavelength for low N and E might be attributed
to the decomposition of -Fe-like crystalline
grains in the surface layer of the ribbons upon
the additional laser-induced quenching of thesurface layer due to short-term laser heating of
the surface and intensive heat removal throughthe bulk of the ribbon. An increase of the laser
irradiation dose makes the conditions of heatremoval from the surface insufficient toprovide a high cooling rate. Then the processesof structure relaxation and crystallization at
the surface have became dominant in this caseand the amount of new -Fe-like crystalline
grains as well as optical conductivity increase
whereas N and E rise.

2b)Fig. 5. Optical conductivity of (Fe0.9Cr0.1)85B15
amorphous metallic ribbons as a function of apulse energy E at constant number of pulses
N=200 (a) and 50 (b).
( ３ － ２ )Rippleeffectsandfurtherdevelopments
It is shown that optical and electronic
properties of surface layers and thin films canbe purposefully changed by variation of thelaser processing modes. The high sensitivity ofellipsometric method to detect opticalanisotropy of the surface layer structure will be
used to diagnostics other materials namely
porous silicon.
［４］Achievements (List of Publications)（10.5
points）（１）T. Aoki, D. Gnatyuk, L. Melnichenko, L.
Poperenko, I. Yurgelevych, Ellipsometric
Diagnostic of Anisotropy Properties of Surface
Layer of Silicon after Laser Treatment, Recent
Advances in Technology Research andEducation. Inter-Academia 2018. Lecture Notes

in Networks and Systems, 53, 66-72 (2019).
（２）M.M. Negrub, D. Hélie, I.V. Yurgelevych,L.V. Poperenko, Ellipsometric control of laser
welded materials, Advances in Intelligent
Systems and Computing, 660, 26-31 (2018).
（3）I. Lyashenko, V. Konovalov, V. Lopatka, L.
Poperenko, I. Ryzhkov, V. Voitsenya, I.
Yurgelevych, Ellipsometric Modification of
Optical Properties of Amorphous Metallic
Mirrors Due to Impact of Deuterium Plasma,
Recent Advances in Technology Research andEducation. Inter-Academia 2018. Lecture Notes
in Networks and Systems, 53, 113-120 (2019).
（ 4 ） R.A. Ryskulov, A.Y. Sribniy, Y.R.
Kovalevskyy, P.O. Kovanzhi, V.M. Prokopets,L.V.
Poperenko,
Automationofspectroellipsometric measurements within
range of 1-4,9 eV by Beattie-Conn method, Proc.
of SPIE, 10672 (2018).
（ 5 ） L.V. Poperenko, V.V. Prorok, S.G.
Rozouvan, I.A. Shaykevich. The role ofmagnetic component of a strong light field inelectrostrictive effect, Semiconductor physics,
quantum electronics and optoelectronics, 21(2), 160-166 (2018).
（ 6 ） D.V. Gnatyuk, L.V. Poperenko, I.V.
Yurgelevych, Ellipsometry of nanostructured Siwafers after femtosecond laser processing, The
19th International Young Scientists Conference“Optics & High Technology Material Science”(SPO 2018), Scientific Works, 2018, Abstract No
BP.6, 113. (25 – 28 October 2018, Kyiv, Ukraine).
（ 7 ） I.V.

Pruskyi,L.V.

Poperenko,

Ye.Yu.Vlasova, I.V. Yurgelevych, Ellipsometricstudy of the graphene film on copper foil, The
19th International Young Scientists Conference“Optics & High Technology Material Science”(SPO 2018), Scientific Works, 2018, Abstract No
AP.22, 85. (25 – 28 October 2018, Kyiv,Ukraine).
（ 8 ） A.O. Shcherbakov, V.G. Kravets, L.V.
Poperenko, Yu.V. Kudryavtsev, I.V. Yurgelevych,
Ellipsometry of graphene-protected structures

based on copper, The 19th International Young
Scientists Conference “Optics & HighTechnology Material Science” (SPO 2018),
Scientific Works, 2018, Abstract No AO.5, 43.
(25 – 28 October 2018, Kyiv, Ukraine).
（ 9 ） L.V. Poperenko, O.A. Akimova, V.M.
Kononenko, O.Y. Meshalkin, O.V. Stronskyi, I.V.
Yurgelevych, Ellipsometric diagnostics ofchalcogenide thin films, The 19th International
Young Scientists Conference “Optics & HighTechnology Material Science” (SPO 2018),
Scientific Works, 2018, Abstract No AP.18, 78.
(25 – 28 October 2018, Kyiv, Ukraine).