Form 1

2018 Report Form for Collaboration with
Research Center for Biomedical Engineering

Acceptance dateYear/month/day
Acceptance
NumberDate: Year/Month Day
2019/03/14/

To Chairman, Board of Directors, Research Center for Biomedical Engineering

ApplicantTitle:
Name:
Address:

V.E. Lashkaryov Institute of Semiconductor Physics of the National
Academy of Sciences of Ukraine
Ph.D., Associate Professor, Senior Scientist
Volodymyr GNATYUKProspekt Nauky 41, Kyiv 03028, UKRAINE

Phone:
Fax:
E-mail:+380 44 5258437, +380 67 3239528+380 44 5258342
gnatyuk@ua.fm

Affiliation:

Report Form for Collaboration Research

Research Theme

Development of Cd(Zn)Te-based X/gamma-ray detectors with high resolution for
security and diagnostics instruments

Research Area

1. Biomaterials
2. Bioengineering
3. Functional molecules
4. Chemistry/Electrical Engineering/Mechanical Engineering/Materials Science

Research Period

From: 14/05/2018

To: 31/03/2019

Applicant Organization
Name

Department

Title

Role

Volodymyr
GNATYUK

Department of Physics of Optoelectronic Devices,
V.E. Lashkaryov Institute of Semiconductor Physics of the
National Academy of Sciences of Ukraine, Kyiv, Ukraine

Ph.D.,
Assoc. Prof.,
Senior Scientist

LeaderSergiyLEVYTSKYI

Department of Physics of Optoelectronic Devices, V.E.
Lashkaryov Institute of Semiconductor Physics of the
National Academy of Sciences of Ukraine, Kyiv, Ukraine

Ph.D.,
Senior Scientist

Participant

Kateryna
ZELENSKA

Faculty of Physics, Taras Shevchenko National University ofKyiv, Kyiv, Ukraine

Ph.D.,Engineer

Participant

Collaboration Partners
in the Research Center

Toru AOKI, Ph.D., Professor
Research Institute of Electronics, Shizuoka University, Japan

Research Results (Including Purpose, Results, Figures, etc.)
1. Introduction
During the last years, we have succeeded in elaboration of CdTe-based high energy radiation detectors.
Owing to support of the Cooperative Research at Research Center of Biomedical Engineering (Research
Projects: H27-46, 2055, 2015 & 2035), over 30 articles and 50 abstracts have been published/prepared in
2015-2019. Almost half of the articles have been made during the implementation of the present Collaboration
Research Project No 2035 (in this 30th fiscal year) [1-15] (“List of Publications” below).
The present project (No 2035) has allowed us to continue the research on development of CdTe Schottky
diodes [1, 3, 6-9, 11-14] as well as CdTe-based barrier structures with a p-n junction formed by laser-induced
doping [2, 4, 10, 15]. Both kinds of diodes have shown promise as X/γ-ray detectors for security and diagnostics
instruments. In the present report, we concentrate on the research devoted to formation of the second type
diodes, i.e. study of laser processing of high-resistivity Cd(Zn)Te and semiconductor-metal interfaces to develop
the techniques of laser doping and metallization of the surface of CdTe crystals [2, 4, 10, 15].
2. Research objectives
The purpose of the collaborative research project has been development of the techniques of formation of
CdTe-based barrier structures for efficient room temperature X/γ-ray detectors with sufficient high resolution
and application of them in security and diagnostic instruments [1-15]. In particular, nanosecond laser processingof CdTe crystals and CdTe-metal interface was employed for doping of a thin semiconductor layer with In andmetallization of the crystal surface to create M-p-n structured diodes sensitive to high energy radiation [2, 4, 10,15]. The research was carried out according to the plan presented in the previous project (No 2015) report.
Several approaches of laser doping of high resistivity p-CdTe semiconductor and metallization of the CdTe
crystal surface were studied employing nanosecond pulses of YAG:Nd or KrF excimer lasers. To obtain theevidences of laser deposition of the contact metal onto the CdTe surface and formation of a thin In-doped CdTe
layer, study the mechanisms of laser actions and estimate the optimal regimes of laser irradiation, CdTe-based
structures were studied by scanning electron microscopy (SEM), synchrotron X-ray photoelectron spectroscopy(XPS), photoconductivity (PC), measurements of I-V characteristics and spectra of radioisotopes [2, 4, 10, 15].
3. CdTe semiconductor samples for investigation
We used detector-grade Cl-compensated (111) oriented p-like CdTe semiconductor produced by Acrorad
Co., Ltd. The single-crystal CdTe ingot grown by the Traveling Heater Method was sliced into wafers whichwere preliminary polished by the manufacturer. Parallelepiped-like CdTe(111) samples with the square of 5 × 5mm2 and thickness of 0.5 mm or 0.75 mm were employed. (Fig. 1).
The electronic parameters of CdTe crystals:
ρ ~ (4-6)×109 Ω·cm; μn = 1100 cm2/V·s,
μp = 100 cm2/V·s, τn = 3 μs, τp = 2 μs.
Fig. 1. Schematic illustration of the CdTe(111)single crystal wafer and its crystalline structure.

4. Techniques of laser doping and metallization of CdTe crystals
Metallization of the surface or doping of a thin region of CdTe crystals were made with the laser-assisted
techniques shown in Fig. 2:
1. Laser irradiation of an In target: laser transfer of a thin In film, pre-deposited on the glass substrate by laser
ablation of an In target irradiated through the glass, on the CdTe surface (a); laser deposition of In on the CdTe
surface by irradiation of an In target through the CdTe crystal (b);2. Activation of the In/CdTe interface by irradiation of CdTe crystals, pre-coated with an In dopant (electrode)
film: from the metal side with a YAG:Nd (λ = 1064 nm) (c) or KrF (λ = 248 nm) (d) laser through thesemiconductor (e).
In case of the technique 1 (Fig. 2(a, b)), pulsed laser deposition of In on the CdTe crystal surface for doping
and contact formation was studied. A pulsed YAG:Nd laser (λ = 1064 nm, t = 8 ns) was employed for ablation ofIn, doping and metallization of the CdTe surface. The whole area the crystal or CdTe-In interface was entirely
irradiated from the glass substrate side (Fig. 2(a)) or CdTe side (Fig. 2(b)) at room temperature.

1

YAG:Nd laser
1064 nm

YAG:Nd laser(a)1064 nmlaser(c)
2 YAG:Nd1064 nm

KrF laser
248 nm(d)Glass plate
Glass plate

In film
CdTe crystal

CdTe crystal

In target

YAG:Nd laser

YAG:Nd laser(b)1064 nm

1064 nm

CdTe crystal(e)
CdTe crystal

In target

In film

Fig. 2. Schematic illustration of the proceduresof laser metallizationand doping of CdTe
crystals.

The glass and CdTe were transparent for λ = 1064 nm therefore, it was possible to irradiate the In target (Fig.
2(a)) or CdTe-In interface (Fig. 2(b)) through the glass substrate or CdTe crystal, respectively and thus, todirectly heat, melt, evaporate and ablate a very thin In layer, and affect the CdTe surface adjoining to the metal.
The doping processes of the thin CdTe region with In atoms, deposition of In islands or film, or evenmetallization of the crystal surface could occur depending on laser power density and number of laser shots.
In the case of the technique 2 (Fig. 2(c-e)), CdTe(111)B crystal surface was preliminary coated with an In
film (100-400 nm) by thermal vacuum evaporation. Irradiation of the In/CdTe structures was carried out in two
ways: (i) from the In-coated side, using pulses of YAG:Nd (λ = 1064 nm, t = 8) or KrF excimer laser (λ = 248
nm; t = 20 ns) (Fig. 2(c, d)); (ii) through the semiconductor, using YAG:Nd laser pulses (Fig. 2(e)). In the lasecase, it was possible directly affect the In/CdTe interface because, laser pulses (λ = 1064 nm) were absorbed
only by a thin In layer adjoining to the CdTe inside the sample (Fig. 2(e)).
5. Results of laser deposition of In on the CdTe crystals

(a)

800

(b)

800

50 μm

50 μm

3800

3800

10 μm

10 μm

Indium islands, deposited by laser
ablation, were revealed on the CdTe surface
by SEM images (Fig. 3a, b), which wereobtained from the samples prepared by thelaser-based techniques shown in Figs. 2(a)and 2(b) respectively. A high contrast isclearly seen between conductive In islands(light areas) and semi-insulating CdTe
semiconductor (dark areas) [4].
Fig. 3. SEM micrographs (magnification is×800 and×3000 at upper and lower row,
respectively) of the In-metallized (In-doped)
CdTe crystal surfaces (a) and (b) obtained withthe laser processing technique shown in Figs.
2(a) & (b), respectively.

The PC spectrum of the CdTe crystals before laser processing had a typical Δ-shape, indicating enhanced
surface recombination in the strong absorption region (Fig. 4, curve 1). Laser treatment (Fig. 2(a)) resulted inincreasing the PC signal and raising the short-wavelength wing of the spectrum (Fig. 4, curve 2). These changes
were evidence of a decrease in the surface recombination velocity in the doped or/and metallized CdTe region
that was attributed to creation of a built-in electric field due to the formation surface barrier structure [4].
The obtained structure demonstrated the rectifying I-V characteristics measured in the dark at room
temperature (20°C) and slightly heated (50°C) (Fig. 5, curves 1 and 5) at applying bias up to V = 20 V. Whenthe sample was illuminated with an incandescent lamp, the energy of charge carriers exceeded the electricalbarrier height and more symmetric I-V characteristics were observed (Fig. 5, curves 3 and 4). A significant
increase in forward and reverse currents was due to a decrease in resistivity of the bulk the In/CdTe structure.
The I-V characteristic of the CdTe sample after laser-induced deposition of In, measured at higher
temperature (T = 50 ºC) also showed rectification properties with a little higher currents according to a typicaltemperature dependence of the semiconductor resistivity (Fig. 5, curve 5).

Current (nA)

1 - initial CdTe crystal
2 - after laser processing
with the technique shownin Fig. 2(a)

0.8
0.6

-20

2
0.2

600

700

-10

14.7 nA (2)31.5 nA (5)

1

500

-15

4

5

300

2

0

1

-5

5

800

900

-300

15

20

(1) - dark, T = 20 oC(2) - light, d = 2 m, T = 20 oC(3) - light, d = 40 cm, T = 20 oC(4) - light, d = 20 cm, T = 20 oC(5) - dark, T = 50 oC-900

Fig. 4. PС spectra of the CdTe crystals before (1) andafter (2) laser deposition of In by the technique Fig. 2(a) .

10Voltage (V)-600

Wavelength (nm)3600

1.3 nA (1)

0.4

0

900

0

Photoconductivity intensity (a.u.)

1.0

Fig. 5. I-V characteristics of the In/CdTe structures
created by the technique Fig. 2(a) (Ag-paste contacts).

The resistance of the metallized CdTe surface region exceeded that of the initial crystals in a few times that
was attributed to formation of micro-diodes, formed by laser-induced creation of n-type micro-regions in thesurface layer of p-CdTe crystals, connected to each other in the opposite direction. This is supported by the
SEM images (Fig. 3(a)) of the CdTe surface after laser processing Fig. 2(a). Separate metalized islands (lightareas) can be considered as local n-type micro-regions at the surface of the semi-insulating p-CdTe crystal [4].
6. Results of XPS study of CdTe crystals after laser-induced doping
The CdTe(111) crystals with a pre-deposited In dopant film (~400 nm), subjected to irradiation with KrF
excimer laser pulses (Fig. 2(d)), were studied by XPS [10]. The XPS spectra of In/CdTe structures wereobtained under irradiation from the In-coated side with a high-spatial resolution X-ray beam of 650 eV using a
synchrotron excitation source [2, 10]. The In film was repeatedly etched 12 times with Ar plasma. Fig. 6 shows
the XPS wide scan spectra of the In/CdTe diode surface before (curve 1) and after Ar-ion etching with different
time (curves 2 and 3), demonstrating the In, Cd and Te features as result of measurement of electron binding
energies. The core level, Auger and valence electron peaks of In, Cd, Te, O and C were used for the detailed
analysis of the component composition of the area adjacent to the In/CdTe interface. As seen, the Te 3d peaks
are absent in the initial In/CdTe structure before etching (Fig. 6, curve 1). They appear after 1 hour etching andincrease with next 1 hour etchings, totally 12 hours of etching (curves 2 and 3). In the behavior of the In 3d andCd 3d peaks with a spin orbital splitting, a decrease of the In 3d and increase in the Cd 3d peak intensities after
each 1 hour Ar-ion etching are observed (Fig. 6, curves 2 and 3). The peaks related to contaminations such as
oxygen (O 1s peak) and carbon (C 1s peak) are manifested in the XPS spectrum of the initial In/CdTe structure(Fig. 6, curves 2 and 1). These features tend to disappear after etching and not observed after multiple etching(Fig. 6, curve 3). This evidenced that contaminations were only on the surface and removed after ion etchings.

0
600

500

400

300

200

100

(c)
(d)

200

(e)
Te 4d
In 4d
Cd 4d

In 3d3/2
In 3d5/2
Cd 3d3/2
Cd 3d5/2
C KLL

O 1s

0.2

(b)

Te MNN2
Te MNN1
In 4s

0.4

Peak area

1 - before etching
2 - after 1 hour etching
3 - after 12 hours etching

0.6

1 - Cd 3d
2 - In 3d

300

In
Cd
Te
O
C

(a)

C 1s
Cd MNN2
Cd MNN1In MNN1

0.8

Core-level
Auger yield Valence band
photoemission yieldyield
Te 3d3/2
Te 3d5/2

Normalized intensity (arb. units)

1.0

100

0

Binding energy (eV)Fig. 6. XPS wide scan spectra of the In/CdTe structure,obtained with the technique Fig. 2(d) after storage (1), andafter etching with Ar ions during 1 hour (2) & 12 hours (3).

0

0

2

4

6

8

10

12

Number of etching

Fig. 7. Dependences of the peak areas in the highresolution Cd 3d (1) and In 3d (2) XPS spectra of the
In/CdTe structure, obtained with the laser processing
technique Fig. 2(d), and subjected to multiple Ar-ion
etching (during 1 hour each), on the number of etching.

Fig. 8. Peak areas from the
XPS spectra of the In 3d5/2(a) and Cd 3d5/2 (b) levels inthe vicinity of the In-CdTe
interface for unirradiatedsample (1), irradiated fromthe In film side (2)(technique Fig. 2(c)) andthrough the CdTe (3)(technique Fig. 2(e)).

Fig. 7 (curves 1 and 2) demonstrates the peak areas calculated from the high resolution XPS spectra for the
Cd 3d and In 3d, respectively in dependence of the number of etching. The minimum value of the In 3d peak
before etching can be attributed to presence of accidental impurities on the surface. Based on the obtained XPS
data, the distribution of In and Cd atoms with the depth of the In/CdTe structure was estimated. Cd atoms wererevealed in the In film superficial layer which was non-contiguous to the CdTe surface.
Fig. 8 shows analysis of the XPS of the M-p-n structured diodes obtained by the technique Fig. 2(c, e) whenirradiation of the In/CdTe structures, using nanosecond pulses of an infrared (YAG:Nd, λ = 1064 nm) laser, wascarried out in two ways: from the In-coated side (c); through the semiconductor (e). The areas of photoelectron
peaks of the In 3d5/2 and Cd 3d5/2 levels for non-irradiated sample (curves 1), irradiated from the In film side
(curve 2) and through the CdTe (curve 3) by 10 infrared laser pulses with power density of 2.5 MW/cm2 after 10hour Ar sputtering of the In film are shown in Fig. 8 (a, b), respectively.
The In 3d5/2 and Cd 3d5/2 peak areas decreased and increased, respectively, with depth after each Ar ion
sputtering procedure which removed a thin layer of the In film (Fig. 8, (a, b,) curves 1)). The observed distribution
can be explained by the steady state diffusion of Cd and In atoms. The In 3d5/2 peak area kept approximately thesame value with the depth (Fig. 8(a), curve 3)). A small amount of Cd atoms distributed in the In film as seen froman increase in the Cd 3d5/2 peak area after ion sputtering of the In film (Fig. 8(b), curve 3). It can be supposed thatlaser-induced melting of In film in the vicinity of the In/CdTe interface and dissolution of CdTe in In occurred.
The Cd 3d5/2 peak area for the sample Fig. 2(c) almost did not change with the depth (Fig. 8(b), curve 2) andcan be explained by propagation of Cd atoms into the In film and homogeneous distribution in a thin layer of the
In film adjoining to the CdTe surface under action of laser-induced stress and shock waves, and laser-stimulated
diffusion. Formation of a large amount of VCd in the CdTe layer adjoining to the In film were considered. The In
3d5/2 peak area for the same sample (Fig. 8(a), curve 2) decreased with depth after each Ar sputtering less than in
the case of the unirradiated sample (Fig. 8(a), curve 1). It can be assumed that some amount of In atoms penetrated
into a CdTe surface layer and solid-phase laser-induced doping occurred.

-200

-150

-100

-50

8000

3
60
6

1
50

Voltage (V)2
3

FWHM = 4.8 %

2

4000
2000
0

2

662 keV

6000

CountsCurrent (A)

7. Characteristics of M-p-n structured In/CdTe/Au diode detectors
I-V characteristics and 137Cs spectra of the In/CdTe/Au diodes Fig. 2(c, e) are shown in Figs. 9 and 10,
respectively. The samples demonstrated low dark reverse currents: 44 nA for the unirradiated sample (curve 1);
3.7 nA for the diode after laser irradiation of the In film (curve 2); 9 nA for the diode after irradiation of the
In/CdTe interface through the CdTe (curve 3) with 10 infrared laser pulses with power density of 2.5 MW/cm2.

40
4

3
20
2

-0.02
FWHM = 6.6 %
0

1

-0.04

Fig. 9. I-V characteristics of the In/CdTe structures before(1) and after laser irradiation of the In film (2) (techniqueFig. 2(c)) and CdTe-In interface (3) (technique Fig. 2(e)).

2000

4000

6000

8000

Channel number

Fig. 10. Spectra of a 137Cs radioisotope taken with
detectors formed by the technique Fig. 2(c) (2) and
Fig. 2(e) (3), respectively, at applied bias of 200 V.

The spectra of a 137Cs radioisotope were taken at room temperature by the In/CdTe/Au diode detectors
obtained by the techniques Fig. 2(c, e) and demonstrated energy resolution (FWHM) of 4.8 % (curve 2) and 6.8 %(curve 3), respectively (Fig. 10). The obtained spectroscopic results have evidenced the promise of the employedlaser assisted techniques for fabrication for X/γ-ray detectors [2].
8. Summary
The attractive approaches to develop laser-assisted techniques of doping of p-CdTe semiconductor andmetallization of the CdTe crystal surface have been proposed employing pulses of YAG:Nd (λ = 1064 nm t = 8ns) or KrF excimer (λ = 248 nm, t = 20 ns) lasers [1, 3, 7, 10]: (i) activation of the CdTe-In interface byirradiation of crystals, pre-coated with an In film: (a) from the metal side or (b) through CdTe; (ii) transfer of athin In film, pre-deposited on the glass substrate by laser ablation of an In target irradiated through the glass, on
the CdTe surface; (iii) deposition of In on the CdTe by irradiation of an In target through the CdTe.
Depending on laser photon energy and irradiation technique, different doping mechanisms were realized: (i,a) solid-phase doping of a CdTe nanolayer by a laser-induced shock wave; (i, b) liquid-phase doping of a thinlayer near the CdTe-metal interface, (ii) and (iii) metallization of the CdTe surface and formation of the impurity
enriched region in CdTe crystals by laser deposition of In.
The evidences of the following effects have been obtained and discussed: (a) laser-induced evaporation of In
film; (b) stress-wave-induced mass transfer; (c) laser-stimulated diffusion; (d) freezing of non-equilibrium
defects; (e) subsequent dissolution of CdTe in the laser-molten thin layer of In film.
The phenomena of abnormally fast laser-stimulated mass transfer and barodiffusion under stress and shockwaves action have been considered as the possible mechanisms of laser-induced doping and migration of In and
Cd atoms in the In/CdTe structure. The experimental direct evidence of incorporation of In dopant atoms into
the surface region of the CdTe crystal and formation of the impurity enriched surface region have been obtainedby the synchrotron XPS spectra measurement [2, 10, 15].
9. Conclusion
The developed techniques of laser-induced doping and metallization of CdTe crystals and formation of
In/CdTe diode structures are promising for fabrication of X/γ-ray detectors. The project research results havebeen presented as 14 reports at the 6 International scientific meetings, published (submitted to publication) in 15
articles including 10 articles with acknowledgment to the project. This collaborative research work has been
performed during the project period (May 2018 – March 2019).
List of Publications Related to the Collaboration Research (1 chapter in the book [7] and 9 articles havebeen published during duration of the Project No 2035 (May 2018 – March 2019) and 5 more articles have been
submitted for publication. 10 articles contain acknowledgments to the Project No 2035).
1.

2.

3.

4.

5.

6.

7.

O. Maslyanchuk, M. Solovan, V. Brus, P. Maryanchuk, E. Maistruk, I. Fodchuk, V. Gnatyuk, T. Aoki,
C. Lambropoulos, C. Potiriadis, Performance comparison of X- and γ-ray CdTe detectors with MoOx, TiOx
and TiN Schottky contacts, IEEE Transactions on Nuclear Science, Vol. 65, Issue 7 (Jul. 2018) 1365-1370. DOI:
10.1109/TNS.2018.2838766.
K. Zelenska, V Gnatyuk, W. Pecharapa, W. Mekprasart, H. Nakajima, Synchrotron radiation X-ray
photoelectron spectroscopic study of CdTe-In structures formed by laser-induced doping technique, AIP
Conference Proceedings, Vol. 2010, Issue 1, (Sep. 2018) 020011-1-5. DOI: 10.1063/1.5053187. (Article withacknowledgment to the Project No 2035).
V. Gnatyuk, V. Sklyarchuk, T. Aoki, A Koike, W. Pecharapa, Development of CdTe-based nuclear radiation
sensors and related devices, AIP Conference Proceedings, Vol. 2010, Issue 1, (Sep. 2018) 020012-1-5. DOI:
10.1063/1.5053188. (Article with acknowledgment to the Project).
K. Zelenska, V. Gnatyuk, V. Veleschuk, T. Aoki, Pulsed laser deposition of indium on the CdTe crystal surface
for contact formation, Proceedings of SPIE, Vol. 10762 (Sep. 2018) 1076218-1-6. DOI: 10.1117/12.2323380.
(Article with acknowledgment to the Project No 2035).
V. Sklyarchuk, V. Gnatyuk, T. Aoki, Hg3In2Te6-based radiation and temperature stable photodetectors,
Infrared Sensors, Devices, and Applications VIII, Proceedings of SPIE, Vol. 10766 (Sep. 2018) 107660R-1-7.
DOI: 10.1117/12.2322518. (Article with acknowledgment to the Project).
V.V. Brus, O.L. Maslyanchuk, M.M. Solovan, P.D. Maryanchuk, I.M. Fodchuk, V.A. Gnatyuk, N.D. Vakhnyak,
S.V. Melnychuk, T. Aoki, Graphene/semi-insulating single crystal CdTe Schottky-type heterojunction X- andγ-ray radiation detectors, Scientific Reports, Vol. 9, No 1 (Jan. 2019) 1065-1-8. DOI: 10.1038/s41598-018-37637-w.
O. Maslyanchuk, S. Melnychuk, V. Gnatyuk, T. Aoki, Mechanisms of charge transport and photoelectric
conversion in CdTe-based X- and gamma-rays detectors, Chapter in the book “New Trends in Nuclear Science”,

27-47, Published: 5th Nov. 2018, ISBN 978-953-51-6756-3, (Ed. Prof. Nasser S. Awwad), IntechOpen Ltd. DOI:
10.5772/intechopen.78504.
8. V. Gnatyuk, V. Sklyarchuk, K. Zelenska, K. Sakaida, T. Terao, T. Aoki, Spectroscopic studies of Ni/CdTe/Au
Schottky diode X/γ-ray detectors, Thai Journal of Nanoscience and Nanotechnology, Vol. 3, Issue 2 (Dec. 2018)12 pages. http://www.nano.kmitl.ac.th/tjnn/index.php/tjnn/article/view/46/39 . (Article with acknowledgment to theProject).
9. V.A. Gnatyuk, K.S. Zelenska, V.M. Sklyarchuk, W. Pecharapa, T. Aoki, Gamma-ray spectroscopic
performance of large-area CdTe-based Schottky diodes, in: G. Laukaitis (eds) Recent Advances in Technology
Research and Education. Inter-Academia 2018. Lecture Notes in Networks and Systems (LNNS), Vol. 53, Cham:
Springer, 2019, pp. 58-65. DOI: 10.1007/978-3-319-99834-3_8. (Article with acknowledgment to the Project).
10. K. Zelenska, V. Gnatyuk, H. Nakajima, W. Mekprasart, W. Pecharapa, XPS study of the In/CdTe interface
modified by nanosecond laser irradiation, in: G. Laukaitis (eds) Recent Advances in Technology Research and
Education. Inter-Academia 2018. Lecture Notes in Networks and Systems, Vol. 53, Cham: Springer, 2019, pp.
73-79. (on line: 19 Aug. 2018). DOI: 10.1007/978-3-319-99834-3_10. (Article with acknowledgment to the Project).
11. V.M. Sklyarchuk, V.A. Gnatyuk, T. Aoki, Depletion region in CdTe Schottky diode X- and γ-ray detectors,
IEEE Transactions on Nuclear Science, (2019) 5 pages. (Article with acknowledgment to the Project), in press.
12. O. Maslyanchuk, M. Solovan, V. Brus, P. Maryanchuk, E. Maistruk, I. Fodchuk, V. Gnatyuk, Charge transport
properties of CdTe X/γ-rays detectors with Ti and TiOx Schottky contacts, IEEE Transactions on Nuclear
Science. (2019) 7 pages, in press.
13. O. Maslyanchuk, M. Solovan, V. Brus, I. Fodchuk, V. Gnatyuk, T. Aoki, Charge transport processes of CdTe
X/γ-rays detectors with TiOx Schottky contacts, 2018 IEEE Nuclear Science Symposium, Medical Imaging
Conference and Room-Temperature Semiconductor Detector Workshop (NSS/MIC/RTSD 2018), Conference
Record, (2019), 6 pages, in press.
14. V.A. Gnatyuk, K.S. Zelenska, V.M. Sklyarchuk, C.P. Lambropoulos, C. Potiriadis, T. Terao, K. Takagi, A. Koike,
T. Aoki, X/γ-ray detector modules with stacked CdTe-based Schottky diodes, 2018 IEEE Nuclear Science
Symposium, Medical Imaging Conference and Room-Temperature Semiconductor Detector Workshop(NSS/MIC/RTSD 2018), Conference Record, (2019) 6 pages. (Article with acknowledgment to the Project No2035), in press.
15. K. Zelenska V. Gnatyuk, H. Nakajima, W. Pecharapa, T. Aoki, Laser doped layer in CdTe diode detectors
revealed by synchrotron XPS, 2018 IEEE Nuclear Science Symposium, Medical Imaging Conference andRoom-Temperature Semiconductor Detector Workshop (NSS/MIC/RTSD 2018), Conference Record, (2019) 4
pages, (Article with acknowledgment to the Project No 2035), in press.

List of Presentations (conferences, meetings, etc.) (related to the results of the Project No 2035)
1. V. Gnatyuk, T. Aoki, A. Koike, Development of CdTe-based nuclear radiation sensors and related devices,
International Conference on Science and Technology of Emerging Materials (STEMa2018), Book of Abstracts,
2018, Abstract No OR-SSM01, 146. (18-20 July 2018, Pattaya, Thailand).
2. K. Zelenska, V. Gnatyuk, W. Pecharapa, H. Nakajima, Synchrotron radiation X-ray photoelectron
spectroscopic study of CdTe-In structures formed by laser-induced doping technique, International
Conference on Science and Technology of Emerging Materials (STEMa2018), Book of Abstracts, 2018, Abstract
No OR-OEM16, 189. (18-20 July 2018, Pattaya, Thailand).
3. K. Zelenska, V. Gnatyuk, T. Aoki, Pulsed laser deposition of indium on the CdTe crystal surface for contact
formation, The conference on Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XX (Conference 10762),
Part of 2018 SPIE Optics + Photonics: Optical Engineering + Applications, Program, 2018, Abstract No
10762-32, 150. (19-23 August 2018, San Diego, CA, USA).
4. V.M. Sklyarchuk, V.A. Gnatyuk, T. Aoki, Hg3In2Te6-based radiation and temperature stable photodetectors,
The conference on Infrared Sensors, Devices, and Applications VIII (Conference 10766), Part of 2018 SPIE
Optics + Photonics: Optical Engineering + Applications, Program, 2018, Abstract No 10766-4, 159. (19-23
August 2018, San Diego, CA, USA).
5. K.S. Zelenska, V.A. Gnatyuk, H. Nakajima, W. Pecharapa, XPS study of the In/CdTe interface modified bynanosecond laser irradiation, The 17th International Conference on Global Research and Education,
Inter-Academia 2018 (iA-2018), Programme & abstracts, 2018, 15. (24-27 September 2018, Kaunas, Lithuania).
6. V.A. Gnatyuk, K.S. Zelenska, V.M. Sklyarchuk, W. Pecharapa, T. Aoki, Gamma-ray spectroscopic
performance of large-area CdTe-based Schottky diodes, The 17th International Conference on Global
Research and Education, Inter-Academia 2018 (iA-2018), Programme & abstracts, 2018, 27. (24-27 September
2018, Kaunas, Lithuania).
7. O. Maslyanchuk, M. Solovan, V. Brus, I. Fodchuk, V. Gnatyuk, T. Aoki, Special features of charge transport in
Ti/CdTe X/γ-rays detectors, VIII Ukrainian Scientific Conference on Physics of Semiconductors (USCPS-8),
Abstracts, 2018, 381-382. (2-4 October 2018, Uzhhorod, Ukraine).
8. O. Maslyanchuk, M. Solovan, V. Brus, I. Fodchuk, V. Gnatyuk, T. Aoki, Charge transport properties of CdTe
X/γ-rays detectors with titanium Schottky contacts, The 25th International Symposium on Room-Temperature
Semiconductor Detectors, 2018 IEEE Nuclear Science Symposium & Medical Imaging Conference (2018 IEEE
NSS/MIC/RTSD), Conf. Program & Abstracts, 2018, Abstract #1196. (10-17 November 2018, Sydney, Australia).
9. T. Aoki, J. Nishizawa, T. Takagi, K. Takagi, T. Terao, V. Gnatyuk, A. Koike, CdTe pn junction type detector
formation by interfacial direct laser irradiation doping, The 25th International Symposium onRoom-Temperature Semiconductor Detectors, 2018 IEEE Nuclear Science Symposium & Medical Imaging
Conference (2018 IEEE NSS/MIC/RTSD), Conf. Program & Abstracts, 2018, Abstract #2805. (10-17 November
2018, Sydney, Australia).
10. V.A. Gnatyuk, K.S. Zelenska, V.M. Sklyarchuk, C.P. Lambropoulos, C. Potiriadis, T. Terao, K. Takagi, A. Koike,
T. Aoki, X/γ-ray detector modules with stacked CdTe-based Schottky diodes, The 25th International
Symposium on Room-Temperature Semiconductor Detectors, 2018 IEEE Nuclear Science Symposium & Medical
Imaging Conference (2018 IEEE NSS/MIC/RTSD), Conf. Program & Abstracts, 2018, Abstract #2913. (10-17
November 2018, Sydney, Australia).
11. K. Zelenska, V. Gnatyuk, H. Nakajima, W. Pecharapa, T. Aoki, Y. Ono, Laser doped layer in CdTe diodedetectors revealed by synchrotron XPS, The 25th International Symposium on Room-Temperature
Semiconductor Detectors, 2018 IEEE Nuclear Science Symposium & Medical Imaging Conference (2018 IEEE
NSS/MIC/RTSD), Conf. Program & Abstracts, 2018, Abstract #2927. (10-17 November 2018, Sydney, Australia).
12. V. Gnatyuk, K. Zelenska, V. Sklyarchuk, T. Aoki, Formation of CdTe-based barrier structures for
X/gamma-ray diode detectors, International Workshop, (25 December 2018, Hamamatsu, Japan).
13. V. Gnatyuk, S. Levytskyi, K. Zelenska, T. Aoki, Development of Cd(Zn)Te-based X/gamma-ray detectors
with high resolution for security and diagnostics instruments, Heisei 30th Biomedicine Dental Engineering
Collaborative Research Base Results Report Meeting, Book of Abstracts, 2019, Poster presentation No 079, 107.
(8 March 2019, Tokyo, Japan).
14. O. Kulyk, V. Tkachenko, O. Podshyvalova, V. Gnatyuk, T. Aoki, Nonlinear waves of elementary step density
on the vicinal surfaces of growth, Heisei 30th Biomedicine Dental Engineering Collaborative Research Base
Results Report Meeting, Book of Abstracts, 2019, Poster presentation No 087, 115. (8 March 2019, Tokyo, Japan).

List of Awards


2 grants of visiting professors: Owing to the obtained results in the frame of the project, two participants(team leader Dr. Volodymyr Gnatyuk and team member Dr. Kateryna Zelenska were awarded by invitedprofessor grants (invitation and financial support) to visit the College of Nanotechnology, King Mongkut's
Institute of Technology Ladkrabang (KMITL), Bangkok, Thailand (July 2018).

Registration of research-theme continuation for next year
Prior consent from the collaboration partner in the Research Center is necessary.

Yes

No

Research plan for the next year (from April 1, 2019 to March 31, 2020), if the collaboration research is continued.
Based on to a huge number of scientific publications (15 articles and 14 abstracts/reports) prepared under the
implementation of the current project (No 2035), i.e. during one year, we can conclude that the field and topic of
the research are very interesting and promising, the achieved results are scientifically and practically significant
and collaborative research work should be continued.
We plan to develop and optimize the techniques of formation of electrical contacts (both Ohmic and Schottky
types) and deposition of electrodes onto CdTe-based semiconductors and other materials (including single crystal
perovskites) which are promising for X/γ-ray detectors.
The advanced techniques based on nanosecond laser irradiation and ion-plasma processing, which have been
partly studied in the current project, will be employed in fabrication of Cd(Zn)Te-based X/γ-ray detectors. Threetechniques of laser-induced doping of the CdTe surface region and creation of In(Al)/CdTe/Au diodes with a p-njunction have been studied and will be used in the next collaborative research project: (i) liquid-phase doping; (ii)solid-phase doping and (iii) space-confined doping. Schottky diodes will be created by deposition of Ni or Cr(rectifying contact) and Au (Ohmic contact) electrodes on the opposite faces of Cd(Zn)Te crystals preliminary
subjected to chemical treatments and/or ion-bombardment. The following research activities are scheduled: to study electrical and photoelectric properties of CdTe-based solid solutions subjected to laser pulse action;
 to elaborate the techniques of deposition (including laser deposition) of metals and carbon-based compounds
on the materials used for X/γ-ray detection in order to form efficient electrical contacts and electrodes;
 to investigate the effect of the thickness of CdTe crystals on detection properties of Schottky diode detectors;
 to study the electronic transport mechanisms in CdTe-based diodes elaborated for X/γ-ray detectors anddevelop the charge transport models for CdTe barrier structures with different electrical contacts; to study electrical characteristics of diode detector structures in the wide range of applied bias voltages;
 to test the fabricated detectors by spectroscopic measurements using various radioisotopes emitting radiationfrom low to high energies of X/γ-ray range.