Impedance anisotropy and quantum photocapacity of bio/inorganic clathrates InSe〈histidine〉 and gase〈histidine〉
Intercalated nanostructures of InSe〈histidine〉 and GaSe〈histidine〉 were formed. Phenomena of the negative capacitance and the quantum capacitance are visualized in the first nanostructure. The introduction of histidine between indium selenide layers leads to increasing of conductivity anisotropy ( σ...
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
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Ivashchyshyn, F.O. Grygorchak, I.I. Klapchuk, M.I. 2017-06-13T17:45:44Z 2017-06-13T17:45:44Z 2015 Impedance anisotropy and quantum photocapacity of bio/inorganic clathrates InSe〈histidine〉 and gase〈histidine〉 / F.O. Ivashchyshyn, I.I. Grygorchak, M.I. Klapchuk // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2015. — Т. 18, № 3. — С. 362-366. — Бібліогр.: 10 назв. — англ. 1560-8034 DOI: 10.15407/spqeo18.03.362 PACS 43.58.Bh, 71.20.Tk https://nasplib.isofts.kiev.ua/handle/123456789/121247 Intercalated nanostructures of InSe〈histidine〉 and GaSe〈histidine〉 were formed. Phenomena of the negative capacitance and the quantum capacitance are visualized in the first nanostructure. The introduction of histidine between indium selenide layers leads to increasing of conductivity anisotropy ( σ|| σ⊥ ) from 67 to 226. Temperature dependences of the real component of the complex impedance indicate semiconductor mechanism of conductivity along nanolayers with two activation energies: 1.6 meV at low-temperature and 0.25 meV in high-temperature regions. Appearance of the giant high-frequency negative magnetoresistance and almost 20-fold photosensitivity increase are observed in the second nanostructure. The conductivity anisotropy of the nanostructure GaSe〈htd〉 ( σ|| σ⊥ ) is 10² . Temperature dependence of the real component of complex impedance along the layers at temperature regions –30 < t °C ≤ 10, 10 < t °C ≤ 30, 30 < t °C ≤ 50 demonstrates cardinally different mechanisms of conductivity. Activation energies are 0.35 meV in the low-temperature and 0.69 meV in high-temperature intervals. Non-activated conductivity mechanism is observed within the range of temperatures 10 < t °C ≤ 30. The parameters of the energy spectrum calculated using the Geballe-Pollak theory prior to and after introduction of histidine for two nanostructures are given; it well correlates with the experimental dates. en Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України Semiconductor Physics Quantum Electronics & Optoelectronics Impedance anisotropy and quantum photocapacity of bio/inorganic clathrates InSe〈histidine〉 and gase〈histidine〉 Article published earlier |
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Impedance anisotropy and quantum photocapacity of bio/inorganic clathrates InSe〈histidine〉 and gase〈histidine〉 |
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Impedance anisotropy and quantum photocapacity of bio/inorganic clathrates InSe〈histidine〉 and gase〈histidine〉 Ivashchyshyn, F.O. Grygorchak, I.I. Klapchuk, M.I. |
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Impedance anisotropy and quantum photocapacity of bio/inorganic clathrates InSe〈histidine〉 and gase〈histidine〉 |
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Impedance anisotropy and quantum photocapacity of bio/inorganic clathrates InSe〈histidine〉 and gase〈histidine〉 |
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Impedance anisotropy and quantum photocapacity of bio/inorganic clathrates InSe〈histidine〉 and gase〈histidine〉 |
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Impedance anisotropy and quantum photocapacity of bio/inorganic clathrates InSe〈histidine〉 and gase〈histidine〉 |
| title_sort |
impedance anisotropy and quantum photocapacity of bio/inorganic clathrates inse〈histidine〉 and gase〈histidine〉 |
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Ivashchyshyn, F.O. Grygorchak, I.I. Klapchuk, M.I. |
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Ivashchyshyn, F.O. Grygorchak, I.I. Klapchuk, M.I. |
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2015 |
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Semiconductor Physics Quantum Electronics & Optoelectronics |
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
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Article |
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Intercalated nanostructures of InSe〈histidine〉 and GaSe〈histidine〉 were formed. Phenomena of the negative capacitance and the quantum capacitance are visualized in the first nanostructure. The introduction of histidine between indium selenide layers leads to increasing of conductivity anisotropy ( σ|| σ⊥ ) from 67 to 226. Temperature dependences of the real component of the complex impedance indicate semiconductor mechanism of conductivity along nanolayers with two activation energies: 1.6 meV at low-temperature and 0.25 meV in high-temperature regions. Appearance of the giant high-frequency negative magnetoresistance and almost 20-fold photosensitivity increase are observed in the second nanostructure. The conductivity anisotropy of the nanostructure GaSe〈htd〉 ( σ|| σ⊥ ) is 10² . Temperature dependence of the real component of complex impedance along the layers at temperature regions –30 < t °C ≤ 10, 10 < t °C ≤ 30, 30 < t °C ≤ 50 demonstrates cardinally different mechanisms of conductivity. Activation energies are 0.35 meV in the low-temperature and 0.69 meV in high-temperature intervals. Non-activated conductivity mechanism is observed within the range of temperatures 10 < t °C ≤ 30. The parameters of the energy spectrum calculated using the Geballe-Pollak theory prior to and after introduction of histidine for two nanostructures are given; it well correlates with the experimental dates.
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1560-8034 |
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https://nasplib.isofts.kiev.ua/handle/123456789/121247 |
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Impedance anisotropy and quantum photocapacity of bio/inorganic clathrates InSe〈histidine〉 and gase〈histidine〉 / F.O. Ivashchyshyn, I.I. Grygorchak, M.I. Klapchuk // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2015. — Т. 18, № 3. — С. 362-366. — Бібліогр.: 10 назв. — англ. |
| work_keys_str_mv |
AT ivashchyshynfo impedanceanisotropyandquantumphotocapacityofbioinorganicclathratesinsehistidineandgasehistidine AT grygorchakii impedanceanisotropyandquantumphotocapacityofbioinorganicclathratesinsehistidineandgasehistidine AT klapchukmi impedanceanisotropyandquantumphotocapacityofbioinorganicclathratesinsehistidineandgasehistidine |
| first_indexed |
2025-11-25T22:46:33Z |
| last_indexed |
2025-11-25T22:46:33Z |
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1850573154561294336 |
| fulltext |
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2015. V. 18, N 3. P. 362-366.
doi: 10.15407/spqeo18.03.362
© 2015, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
362
PACS 43.58.Bh, 71.20.Tk
Impedance anisotropy and quantum photocapacity of bio/inorganic
clathrates InSe〈histidine〉 and gase〈histidine〉
F.O. Ivashchyshyn, I.I. Grygorchak, M.I. Klapchuk
Lviv Polytechnic National University, 12, S. Bandera str., 79013 Lviv, Ukraine
E-mail: Fivash@i.ua, Ivan_gryg@ukr.net, M.klapchuk@gmail.com
Abstract. Intercalated nanostructures of InSe〈histidine〉 and GaSe〈histidine〉 were
formed. Phenomena of the negative capacitance and the quantum capacitance are
visualized in the first nanostructure. The introduction of histidine between indium
selenide layers leads to increasing of conductivity anisotropy ( ⊥σσ|| ) from 67 to 226.
Temperature dependences of the real component of the complex impedance indicate
semiconductor mechanism of conductivity along nanolayers with two activation
energies: 1.6 meV at low-temperature and 0.25 meV in high-temperature regions.
Appearance of the giant high-frequency negative magnetoresistance and almost 20-fold
photosensitivity increase are observed in the second nanostructure. The conductivity
anisotropy of the nanostructure GaSe〈htd〉 ( ⊥σσ|| ) is 102. Temperature dependence of
the real component of complex impedance along the layers at temperature regions
–30 < t °C ≤ 10, 10 < t °C ≤ 30, 30 < t °C ≤ 50 demonstrates cardinally different
mechanisms of conductivity. Activation energies are 0.35 meV in the low-temperature
and 0.69 meV in high-temperature intervals. Non-activated conductivity mechanism is
observed within the range of temperatures 10 < t °C ≤ 30. The parameters of the energy
spectrum calculated using the Geballe-Pollak theory prior to and after introduction of
histidine for two nanostructures are given; it well correlates with the experimental dates.
Keywords: InSe, GaSe, histidine, supramolecular structure, intercalation, impedance
spectroscopy, Nyquist diagram.
Manuscript received 28.04.15; revised version received 29.07.15; accepted for
publication 03.09.15; published online 30.09.15.
1. Introduction
With rapid development of nanoengineering
(nanoelectronics, quantum coherent spinotronics, etc.)
and with related to these sciences necessity to initiate
creation of super-high capacitance accumulators of
electric energy, formation of heterostructured inorganic-
inorganic, inorganic-organic, and bio-organic materials
attract still more attention of scientists. The ability to
realize unique physical and chemical properties [1, 2],
sometimes paradoxical, is associated with these
materials.
The known methods of obtaining them, such as
vacuum deposition, photolithography, synthetical Lan-
guir-Blodgett techniques, have some limitations caused
by limited variability of the choice of different hetero-
ingredients and by problematic synthesis of “host-guest”
configuration, especially synthesis of heteroagregatic
ones. By this time only a small experience gained on this
way and made small steps [3, 4]. As far as bionanosemi-
conductor inorganic multilayered nanohybrids are con-
cerned, nowadays, information on these investigations is
lacking at all. Therefore, the aim of this work is to fill, to
some extent, the gap in this branch of investigations.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2015. V. 18, N 3. P. 362-366.
doi: 10.15407/spqeo18.03.362
© 2015, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
363
2. Results and discussions
To form bio-inorganic/semiconductor nanohybrids, the
layered crystals of gallium selenide (GaSe) and indium
selenide (InSe) were used as semiconductor matrix and
the aminoacid histidine (C6H9N3O2) was chosen as a
biologically active guest element. The suggested three-
stage scheme of nanoengineering of crystals was used in
[5]. The main feature of histidine is that it is a zwitteron
(i.e., it possesses properties of both anion and cation)
with a colossal dipole moment.
Formation of the histidine nanolayers in a three-
fold expanded matrix of indium selenide leads to more
than forty-fold increasing the real component of specific
complex impedance and to almost four-fold increasing
the photosensitivity in the direction perpendicular to the
plane of nanolayers.
At the same time, the effect of photoinduced
“negative capacitance” is observed: the corresponding
low-frequency impedance hodograph branch enters the
fourth, inductive quadrant of the complex impedance
plane, which correlates with the low-frequency
oscillation Re Z(ω) under illumination (see curve 6 in
Fig. 1). In this case, the mechanism of negative
photocapacitance is most likely associated with the
photoexcitation of electrons from occupied states below
the Fermi level and, therefore, with formation of trap
centers for injected electrons with the relaxation time
longer than the half-period of a sinusoidal signal.
According to it, the equivalent electric circuit can
be represented that shown in Fig. 2. The first parallel
high-frequency link R1//CPE1 (where CPE1 is element of
constant phase capacitive type [6]) in the circuit models
the distributed capacitance caused by the presence of
vacancies or impurity defects that provide electronic
conductivity at room temperature. Second R2//CPE2, the
middle-frequency link, displays the path of current flow
through energy barriers in guest positions. The low-
frequency link СQ //RrecL models the path current flow
through the boundary of histidine/semiconductor matrix.
Here, Rrec is the resistance recombination that simulates
a barrier to charge СQ, L – inductance, СQ – quantum
capacitance [7] that is described by the equation
nQ dEdneC F
2= , where n is the concentration of
electrons, EFn – energy of the electron Fermi quasi-level.
For the latter branch of the low-frequency section, the
admittance can be written as follows:
( ) Ci
R
Y
rec
ω−=ω
1 , (1)
where С = СL – CQ, 2
recL RLC = .
According to equation (1), impedance of latter link
in an equivalent electric circuit for an illuminated
nanohybrid at very low frequencies ⎟⎟
⎠
⎞
⎜⎜
⎝
⎛
<ω
CRrec
1 is a
parallel connection of the recombination resistance and
constant negative capacitance C. Note that under
condition СL > CQ the low-frequency branch comes to
the IV inductive quadrant, showing inductive response.
Table 1 shows the parameters of the band spectrum prior
to and after introduction of histidine in InSe, calculated
using the Geballe-Pollak theory. It is evident that
histidine encapsulation reduces the density of states at
the Fermi level by an order of magnitude, which well
correlates with low-frequency areas of Re Z(ω), at the
same time, significantly reducing the distribution of trap
centers. The radius of jump can be considered as a
constant.
Research of the path current flow along the layers
of expanded matrix InSe and nanohybridized structure
InSe〈htd〉 within the frequency range (10–3…1 Hz)
showed that the conductivity anisotropy ( ⊥σσ|| ) with
introduction of histidine increases from 67 to 226.
The growth of Re Z(ω) perpendicular to the
nanolayers after the introduction of histidine may be
caused by decreasing of carrier mobility due to
“rotational” polaron formation, and its falling along
them likely caused by the increasing carrier
concentration due to modification of the InSe band
structure by electric field of “guest” assuming
“ferroelectric” ordering of histidine dipoles along layers,
as shown in Fig. 3a.
Fig. 1. Frequency dependences of complex impedance in per-
pendicular to the nanolayers of expanded matrix InSe (1-3) and
of nanostructure InSe〈htd〉 (4-6), and along layers InSe〈htd〉 (7-
9) measured in the dark (1, 4, 7), as well as under illumination
(3, 6, 9), measured at the action of magnetic field (2, 5, 8).
Fig. 2. The equivalent electric circuit.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2015. V. 18, N 3. P. 362-366.
doi: 10.15407/spqeo18.03.362
© 2015, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
364
a b
Fig. 3. Ferroelectric arrangement of dipoles (a) and the
schematic presentation of band structure modification of
InSe〈htd〉 layers (b).
As shown in our work [8], for the latter case along
the q-axis of the Brillouin zone the valence band splits
into two subbands, at the same time widths of subbands
reduce comparatively to the unperturbed system.
A similar situation for the conduction band can be
obtained. As a result, one of the branches of the valence
band arises along the energy scale “up” and one of the
branches of the conduction band goes “down” (Fig. 3b).
As a consequence, the effective bandgap decreases, or
conduction band catch the Fermi level, which leads to
increasing of the concentration of carriers.
Photosensitivity along layers of InSe〈htd〉 is almost
twice less than that in perpendicular to them, while for
the expanded matrix these values are virtually identical.
When illuminating, we observe an anomalous frequency
dependence Re Z(ω): it is the monotonic growth with
increasing frequency in fairly wide frequency range
(curve 9 in Fig. 1). In this case, low-frequency branch
of the impedance hodograph is almost parallel to Re Z
axis with its opposite genesis ω, as well as to the
relevant branch of hodograph built to measure in the
dark. If the latter are modeled by finite element of
constant phase (BCPE) [6], which reflects the path
current flow in space-restricted area with the complex
electrical conductivity, then under illumination one can
propose a model of impedance along the layers con-
taining the link with quantum capacity (Lurie [7]). In
this case, it represents contribution from the histidine
nanoclusters with the energy spectrum of the path
current flow caused by the non-equilibrium carriers. As
a result, the conductivity of non-equilibrium carriers due
to gravity in accordance with the [9] should decrease
with increasing the frequency, as observed in Fig. 1
(curve 3).
Temperature dependences of the real component of
the complex impedance along the layers (Fig. 4) indicate
semiconductor nature of the electrical conductivity of
nanohybrids with two activation energies: 1.6 meV in
low-temperature and 0.25 meV in high-temperature
regions. It is interesting to note that, for proper
temperature, the change of conductivity mechanism at
(–10 °C) corresponds to a radical change of the low-
frequency branch in Nyquist diagrams: transfert to the
fourth, inductive quadrant (inset to Fig. 4). It makes the
base to assume that at temperatures higher than –10 °C
captured by trap centers electrons would be delocalized.
When reducing the temperature down to –30 °C,
localized electrons are no longer delocalized in the tails
of the density-of-states.
For the initial expanded matrix (curve 1 in Fig. 5),
we have a usual situation: the corresponding hodograph
of impedance is of two-arc form, and it represents the
capacitive response of localized states and the
frequency-dependent impedance proper caused by jumps
between localized states near the Fermi level in the
packet of atomic monolayers (high-frequency curve).
The middle-frequency curve represents the path of
current flow through widened spaces of actions of van
der Waals forces. These arcs are modeled by means of
BCPE, which represents the path of current flow in
space-restricted domain of complex-valued electric
conductance [10]. The low-frequency section represents
distribution of active resistance element (caused by
discretization of the energy spectrum of the expanded
matrix of gallium selenide), this resistance is modeled by
means of CPE with a low value of phase deviation
ζ < 0.1 [6].
Fig. 4. Temperature dependences of the real component of
impedance along nanolayers InSe〈htd〉. In the inset to Fig. 4
hodograph of impedance is given.
Fig 5. Nyquist diagram measured in the dark for the initial
expanded matrix GaSe (1), and for the nanostructure GaSe〈htd〉
(2) and equivalent electric circuits corresponding to them.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2015. V. 18, N 3. P. 362-366.
doi: 10.15407/spqeo18.03.362
© 2015, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
365
In this case, the equivalent electric circuit is given
in the inset a to Fig. 5. Introduction of histidine leads to
the increase in frequency dispersion of the impedance
hodograph, and it indicates the emergence of additional
potential barriers. Accordingly, the equivalent electric
circuit is like to that shown in that inset b in Fig. 5. The
latter link contains induction (inset b in Fig. 5) because
the low-frequency branch of Nyquist diagram passes to
the induction quadrant IV of the plane of complex-
valued impedance. It indicates phenomenon of a
“negative capacitance”.
Introduction of histidine between selenide layers
leads to twenty-fold growth of the real component of
complex impedance in the low-frequency spectrum
(10–3…1 Hz) (Fig. 6). Lighting nanostructures GaSe〈htd〉
causes a decrease Re Z(ω) almost 5·103 times in the
specified frequency range (curve 4 in Fig. 6). The latter
phenomenon is quite expected, since this semiconductor
matrix is photosensitive in the visible spectrum.
However, compared to the enhanced matrix imple-
mentation histidine leads to an almost 20-fold increase in
photosensitivity. At the same time, Fig. 6 (curve 4)
shows the previously non-observed effect of the giant
high-frequency negative magnetoresistance: in the
frequency range 60 < ω ≤ 106 Hz, the magnetic field
2.75 kОе at room temperature leads to a more than five-
fold reduction of Re Z(ω). Taking into account no
practical visualization of the magnetoresistance at lower
frequencies this effect can most likely be associated with
Zeeman delocalization of charge carriers from the deeper
trap centers. Table 2 shows the parameters of the energy
spectrum before and after introduction of histidine in
GaSe, calculated using the Geballe-Pollak theory. In
contrast to InSe, one can see a decrease of density of
jumping centers and distribution of trap levels near the
Fermi level.
Behavior of hodograph of impedance along the
impedance layers GaSe〈htd〉 has the same character as in
the measurement perpendicular, with the exception of
the magnetic field. In this case, the frequency dispersion
grows and middle/high-frequency branches of Nyquist
diagrams “pass” to the inductive quadrant in the plane of
complex-valued impedance (see the inset to Fig. 7). To
some extent, it correlates with the above discussed
Zeeman localization/delocalization of charge carriers.
Research of the current flow path along the layers
of nanohybridized structure GaSe〈htd〉 showed that
within the frequency range (10–3…1 Hz) the electrical
conductivity anisotropy is 2
|| 10≈σσ ⊥ , and reduction
of the real component of the complex impedance under
illumination reaches the ten-fold value. In contrast to the
previous measurement geometry, in this case positive
magnetoresistance is visualized at lower frequencies
from 10–2 Hz: Re Z(ω) in a magnetic field is growing
more than twice. In this case high-frequency negative
magnetoresistance in the same frequency range not only
preserved, but increasing reaches almost 14-fold value.
Fig. 6. Frequency dependences of the real component of
impedance in perpendicular to the layers for initial expanded
matrix GaSe measured in the dark (1) and for nanostructure
GaSe〈htd〉 measured in the dark (2), as well as under
illumination (4), measured at the action of magnetic field (3).
Fig. 7. Nyquist diagram GaSe〈htd〉 for the perpendicular to the
layers and along them (see inset).
Fig. 8. Temperature dependences of the real component of
impedance along nanolayers GaSe〈htd〉. On the inset, their
frequency dependences are given.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2015. V. 18, N 3. P. 362-366.
doi: 10.15407/spqeo18.03.362
© 2015, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
366
Table 1. The parameters of the band spectrum prior to and
after introduction of histidine in InSe.
Density of
jumping
centers near
the Fermi
level,
N(F)·1044,
J–1m–1
Radius
of
jump
R·10–8,
m
The distri-
bution of
trap cen-
ters near
the Fermi
level,
J·10–23, J
Real
density
of deep
trap
centers
Nt·1022,
m–3
InSe 32.13 2.90 0.61 1.96
InSe〈htd〉 2.32 2.39 15.07 3.50
Table 2. The parameters of the energy spectrum prior to
and after introduction of histidine in GaSe.
Density of
jumping
centers
near the
Fermi
level,
N(F)·1043,
J–1m–1
Radius
of
jump
R·10–8,
m
The distri-
bution of
trap cen-
ters near
the Fermi
level,
J·10–22, J
Real
density
of deep
trap
centers
Nt·1022,
m–3
GaSe 6.56 3.02 2.63 1.73
GaSe〈htd〉 10.60 2.83 1.99 2.10
Obviously, it is indicative of different energy structure in
perpendicular and along the layers direction.
The temperature dependence of GaSe〈htd〉 along
the layers demonstrates cardinally different mechanisms
of conductivity within the temperature regions
–30 < t °C ≤ 10, 10 < t °C ≤ 30, 30 < t °C ≤ 50 (Fig. 8).
If the first and last temperature ranges correspond to the
activation mechanism, then one can obtain non-
activation mechanism of conductivity within the range
of temperatures 10 < t °C ≤ 30.
3. Conclusions
1. Introduction of histidine in the three-fold expanded
matrix of indium selenide leads to the forty-fold
increase of a real component of specific complex
impedance and almost four-fold increase in
photosensitivity in the direction perpendicular to
nanolayers.
2. Appearance of photoinductive “negative photo-
capacitance” is observed for nanostructure
InSe〈htd〉; the mechanism of this phenomenon is a
most likely associated with the photoexcitation of
electrons from occupied states below the Fermi
level and, therefore, with formation of trap centers
for injected electrons with the relaxation time
greater than the half-period of the sinusoidal signal.
3. The conductivity anisotropy ( ⊥σσ|| ) due to
introduction of histidine in extended matrix of
InSe〈htd〉 increases from 67 to 226 within the
frequency range (10–3…1 Hz).
4. Temperature dependence of a conductivity of
nanostructure InSe〈htd〉 has a semiconductor
character with two activation energies 1.6 and
0.25 meV.
5. The introduction of histidine in three-fold expanded
matrix of gallium selenide leads to the twenty-fold
increase of a real component of specific complex
impedance and the twenty-fold one for
photosensitivity in the direction perpendicular to
nanolayers.
6. The evidence of a giant high-frequency negative
magnetoresistance is obtained for the nanostructure
GaSe〈htd〉 in the constant magnetic field 2.75 kОе
at room temperature; magnetic field leads to a more
than 5-fold reduction of Re Z(ω) within the
frequency range 60 < ω ≤ 106 Hz.
7. The conductivity anisotropy ( ⊥σσ|| ) for the
nanostructure GaSe〈htd〉 is 102, and decrease of a
real component of the complex impedance under
illumination reaches the ten-fold value. At the same
time, positive magnetoresistance is visualized at
frequencies less than 10–2 Hz: Re Z(ω) growth
more than twice in magnetic field, and high-
frequency negative magnetoresistance growth
reaching almost 14-fold value.
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