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1.
Vijayaharan A. Venugopal Giampiero Ottaviani Camillo Bresolin Davide Erbetta Alberto Modelli Enrico Varesi 《Journal of Electronic Materials》2009,38(10):2063-2068
The thermal stability of a Ge2Sb2Te5 chalcogenide layer in contact with titanium and titanium nitride metallic thin films has been investigated mainly using x-ray
diffraction and elastic nuclear backscattering techniques. Without breaking vacuum, Ti and TiN have been deposited on Ge2Sb2Te5 material using magnetron sputtering. Thermal treatments have been performed in a 10−7 mbar vacuum furnace. On annealing up to 450°C, the TiN metallic film does not interact with the chalcogenide film, but at
the same time adhesion problems and instabilities in contact resistance arise. To improve the adhesion and eventually stabilize
the contact resistance, an interfacial Ti layer has been considered. At 300°C, a TiTe2 compound is formed by interacting with Te segregated from the Ge2Sb2Te5 layer. At higher temperatures, the Ti layer decomposes the chalcogenide film, forming several compounds tentatively identified
as GeTe, Ge3Ti5, Ge5Ti6, TiTe2,, and Sb2Te3. It has been found that the properties of the Ge2Sb2Te5 film can be retained by controlling the decomposition rate of the chalcogenide layer, which is achieved by providing a limited
supply of Ti and/or by depositing a Te-rich Ge2Sb2Te5 film. 相似文献
2.
Yunfeng Lai Baowei Qiao Jie Feng Yun Ling Lianzhang Lai Yinyin Lin Ting’ao Tang Bingchu Cai Bomy Chen 《Journal of Electronic Materials》2005,34(2):176-181
Nitrogen-doped Ge2Sb2Te5 (GST) films for nonvolatile memories were prepared by reactive sputtering with a GST alloy target. Doped nitrogen content
was determined by using x-ray photoelectron spectroscopy (XPS). The crystallization behavior of the films was investigated
by analyzing x-ray diffraction (XRD) and differential scanning calorimetry (DSC). Results show that nitrogen doping increases
crystallization temperature, crystallization-activation energy, and phase transformation temperature from fcc to hexagonal
(hex) structure. Doped nitrogen probably exists in the grain vacancies or grain boundaries and suppresses grain growth. The
electrical properties of the films were studied by analyzing the optical band gap and the dependence of the resistivity on
the annealing temperature. The optical band gap of the nitrogen-doped GST film is slightly larger than that of the pure GST
film. Energy band theory is used to analyze the effect of doped nitrogen on electrical properties of GST films. Studies reveal
that nitrogen doping increases resistivity and produces three relatively stable resistivity states in the plot of resistivity
versus annealing temperature, which makes GST-based multilevel storage possible. Current-voltage (I-V) characteristics of
the devices show that nitrogen doping increases the memory’s dynamic resistance, which reduces writing current from milliampere
to microampere. 相似文献
3.
É. A. Lebedev S. A. Kozykhin N. N. Konstantinova L. P. Kazakova 《Semiconductors》2009,43(10):1343-1346
Effect of high electric fields on the conductivity of 0.5-1-μm-thick layers of a chalcogenide glassy semiconductor with a
composition Ge2Sb2Te5, used in phase memory cells, has been studied. It was found that two dependences are observed in high fields: dependence
of the current I on the voltage U, of the type I ∝ U
n
, with the exponent (n ≈ 2) related to space-charge-limited currents, and a dependence of the conductivity σ on the field strength F of the type σ = σ0exp(F/F
0) (where F
0 = 6 × 104 V cm−1), caused by ionization of localized states. A mobility of 10−3–10−2 cm2 V−1 s−1 was determined from the space-charge-limited currents. 相似文献
4.
S. A. Kozyukhin A. S. Kuz’minykh A. Yu. Mityagin B. V. Khlopov G. V. Chucheva 《Journal of Communications Technology and Electronics》2011,56(2):188-191
Experimental results on the switching effects related to the phase transitions in Ge2Sb2Te5 in the presence of external voltage or laser irradiation are presented. An electron model of the reversible switching is
discussed. 相似文献
5.
Sang-Ouk Ryu 《Journal of Electronic Materials》2008,37(4):535-539
A phase-change memory device that utilizes an antimony (Sb)-excess Ge15Sb47Te38 chalcogenide thin film was fabricated and its electrical properties were measured and compared with a similar device that
uses Ge22Sb22Te56. The resulting electrical characteristics exhibited I
reset values of 14 mA for Ge22Sb22Te56 and 10.6 mA for Ge15Sb47Te38. Also, the set operation time (t
set) for the device using Ge15Sb47Te38 films was 140 ns, which was more than twice as fast as the Ge22Sb22Te56 device. The relationship between the microstructure and the improved electrical performance of the device was examined by
means of transmission electron microscopy (TEM). 相似文献
6.
A. P. Avachev S. P. Vikhrov N. V. Vishnyakov S. A. Kozyukhin K. V. Mitrofanov E. I. Terukov 《Semiconductors》2012,46(5):591-594
Data on the Raman spectra of thin Ge2Sb2Te5 chalcogenide semiconductor films are reported. The study is performed with the purpose of determining the temperatures of
phase transitions initiated by laser radiation. 相似文献
7.
Takashi Hamachiyo Maki Ashida Kazuhiro Hasezaki 《Journal of Electronic Materials》2009,38(7):1048-1051
A fine measurement system for measuring thermal conductivity was constructed. An accuracy of 1% was determined for the reference
quartz with a value of 1.411 W/m K. Bi0.5Sb1.5Te3 samples were prepared by mechanical alloying followed by hot-pressing. Grain sizes were varied in the range from 1 μm to 10 μm by controlling the sintering temperature in the temperature range from 623 K to 773 K. The thermal conductivity was 0.89 W/m K
for the sample sintered at 623 K, while a grain size of 1.75 μm was measured by optical microscopy and scanning electron microscopy. The thermal conductivity increased on the sample sintered
at 673 K because of grain growth and decreased on those sintered at the temperatures from 673 K to 773 K because the increase
of pore size caused to decrease thermal conductivity. The increase of thermal conductivity for the samples sintered at temperatures
above 773 K was affected by the increase of carrier concentration. 相似文献
8.
S. A. Nemov G. L. Tarantasov V. I. Proshin M. K. Zhitinskaya L. D. Ivanova Yu. V. Granatkina 《Semiconductors》2009,43(12):1585-1589
On one Sb2Te3 single crystal, the temperature dependences of all three independent components of the Nernst-Ettingshausen tensor (Q
ikl
) are measured in the temperature range of 85–450 K, all three components being negative. Alongside with the Nernst-Ettingshausen
effect, the anisotropy of the Hall (R
ikl
) and Seebeck (S
ij
) coefficients and the conductivity (σ
ii
) is also investigated. The carried-out analysis of the experimental data on the Nernst-Ettingshausen and Seebeck effects
indicates that there is the mixed scattering mechanism with the participation of acoustic phonons and impurity ions, the relative
contributions of these mechanisms varying with temperature. In the relaxation-time-tensor approximation, the values of the
effective scattering parameter (r) are determined. The obtained values point to the dominant scattering at acoustic phonons in the cleavage plane and to the
substantial contribution of charged ions to the scattering along the trigonal axis c
3. It is shown that it is possible to explain the major features of experimental data on the Nernst-Ettingshausen effect within
the two-valence-band model with the participation of several groups of holes in the transport phenomena. 相似文献
9.
A thermopile sensor was processed on a glass substrate by electrodeposition of n-type bismuth telluride (Bi-Te) and p-type antimony telluride (Sb-Te) films. The n-type Bi-Te film electrodeposited at −50 mV in a 50 mM electrolyte with a Bi/(Bi + Te) mole ratio of 0.5 exhibited a Seebeck
coefficient of −51.6 μV/K and a power factor of 7.1 × 10−4 W/K2 · m. The p-type Sb-Te film electroplated at 20 mV in a 70 mM solution with an Sb/(Sb + Te) mole ratio of 0.9 exhibited a Seebeck coefficient
of 52.1 μV/K and a power factor of 1.7 × 10−4 W/K2 · m. A thermopile sensor composed of 196 pairs of the p-type Sb-Te and the n-type Bi-Te thin-film legs exhibited sensitivity of 7.3 mV/K. 相似文献
10.
Huqin Zhang Jian He Bo Zhang Zhe Su Terry M. Tritt Navid Soheilnia Holger Kleinke 《Journal of Electronic Materials》2007,36(7):727-731
Mo3Sb7, crystallizing in the Ir3Ge7 type structure, has poor thermoelectric (TE) properties due to its metallic behavior. However, by a partial Sb-Te exchange,
it becomes semiconducting without noticeable structure changes and so achieves a significant enhancement in the thermopower
with the composition of Mo3Sb5Te2. Meanwhile, large cubic voids in the Mo3Sb5Te2 crystal structure provide the possibility of filling the voids with small cations to decrease the thermal conductivity by
the so-called rattling effect. As part of the effort to verify this idea, we report herein the growth as well as measurements
of the thermal and electrical transport properties of Mo3Sb5.4Te1.6 and Ni0.06Mo3Sb5.4Te1.6. 相似文献
11.
K. Rothe M. Stordeur F. Heyroth F. Syrowatka H. S. Leipner 《Journal of Electronic Materials》2010,39(9):1408-1412
A recent trend in thermoelectrics is miniaturization of generators or Peltier coolers using the broad spectrum of thin-film
and nanotechnologies. Power supplies for energy self-sufficient micro and sensor systems are a wide application field for
such generators. It is well known that thermal treatment of as-deposited p-type (Bi0.15Sb0.85)2Te3 films leads to enhancement of their power factors. Whereas up to now only the start (as-deposited) and the end (after annealing)
film stages were investigated, herein for the first time, the dynamical changes of sputter-deposited film properties have
been observed by real-time measurements. The electrical conductivity shows a distinct, irreversible increase during a thermal
cycle of heating to about 320°C followed by cooling to room temperature. The interpretation of the Seebeck and Hall coefficients
points to an enhancement in Hall mobility after annealing. In situ x-ray diffractometry shows the generation of an additional Te phase depending on temperature. This is also confirmed by energy-dispersive
x-ray microanalysis and the corresponding mapping by scanning electron microscopy. It is presumed that the Te enrichment in
a separate, locally well-defined phase is the reason for the improvement in the integral film transport properties. 相似文献
12.
Chang-eun Kim Ken Kurosaki Manabu Ishimaru Hiroaki Muta Shinsuke Yamanaka 《Journal of Electronic Materials》2011,40(5):999-1004
Our group has focused attention on Ga2Te3 as a natural nanostructured thermoelectric material. Ga2Te3 has basically a zincblende structure, but one-third of the Ga sites are structural vacancies due to the valence mismatch
between Ga and Te. It has been confirmed that (1) vacancies in Ga2Te3 exist as two-dimensional (2D) vacancy planes, and (2) Ga2Te3 exhibits an unexpectedly low thermal conductivity (κ), most likely due to highly effective phonon scattering by the 2D vacancy planes. However, the effect of the size and periodicity
of the 2D vacancy planes on κ has been unclear. In addition, it has also been unclear whether only the 2D vacancy planes reduce κ or if point-type vacancies can also reduce κ. In the present study, we tried to prepare Ga2Te3 and Ga2Se3 with various vacancy distributions by controlling annealing conditions. The atomic structures of the samples were characterized
by means of transmission electron microscopy, and κ was evaluated from the thermal diffusivity measured by the laser flash method. The effects of vacancy distributions on κ of Ga2Te3 and Ga2Se3 are discussed. 相似文献
13.
Jan D. König M. Winkler S. Buller W. Bensch U. Schürmann L. Kienle H. Böttner 《Journal of Electronic Materials》2011,40(5):1266-1270
In this work, Bi2Te3-Sb2Te3 superlattices were prepared by the nanoalloying approach. Very thin layers of Bi, Sb, and Te were deposited on cold substrates,
rebuilding the crystal structure of V2VI3 compounds. Nanoalloyed super- lattices consisting of alternating Bi2Te3 and Sb2Te3 layers were grown with a thickness of 9 nm for the individual layers. The as-grown layers were annealed under different conditions
to optimize the thermoelectric parameters. The obtained layers were investigated in their as-grown and annealed states using
x-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive x-ray (EDX) spectroscopy, transmission electron
microscopy (TEM), and electrical measurements. A lower limit of the elemental layer thickness was found to have c-orientation. Pure nanoalloyed Sb2Te3 layers were p-type as expected; however, it was impossible to synthesize p-type Bi2Te3 layers. Hence the Bi2Te3-Sb2Te3 superlattices consisting of alternating n- and p-type layers showed poor thermoelectric properties. 相似文献
14.
The magnetic susceptibility of Czochralski-grown single crystals of Bi2Te3-Sb2Te3 alloys containing 0, 10, 25, 40, 50, 60, 65, 70, 80, 90, 99.5, or 100 mol % Sb2Te3 has been investigated. The magnetic susceptibility of these crystals was determined at the temperature T = 291 K and the magnetic field H oriented parallel (χ‖) and perpendicularly (χ⊥) to the trigonal crystallographic axis C 3. A complicated concentration dependence of the anisotropy of magnetic susceptibility χ‖/χ⊥ has been revealed. The crystals with the free carrier concentration p ≈ 5 × 1019 cm?3 do not exhibit anisotropy of magnetic susceptibility. The transition to the isotropic magnetic state occurs for the compositions characterized by a significantly increased (from 200 to 300 meV) optical bandgap. 相似文献
15.
A. A. Kudryashov V. G. Kytin R. A. Lunin V. A. Kulbachinskii A. Banerjee 《Semiconductors》2016,50(7):869-875
The Shubnikov–de Haas effect and the Hall effect in n-Bi2–xTlxSe3 (x = 0, 0.01, 0.02, 0.04) and p-Sb2–xTlxTe3 (x = 0, 0.005, 0.015, 0.05) single crystals are studied. The carrier mobilities and their changes upon Tl doping are calculated by the Fourier spectra of oscillations. It is found shown that Tl doping decreases the electron concentration in n-Bi2–xTlxSe3 and increases the electron mobility. In p-Sb2–xTlxTe3, both the hole concentration and mobility decrease upon Tl doping. The change in the crystal defect concentration, which leads to these effects, is discussed. 相似文献
16.
O. G. Grushka S. M. Chupyra O. M. Myslyuk S. V. Bilichuk I. I. Zabolotsky 《Semiconductors》2011,45(1):49-51
The effect of electric field and temperature on the conductivity of bulk Hg3In2Te6 crystals is investigated. It is shown that the I–V characteristics in high electric fields are of the S type with the effect of switching into a low-resistance state. The critical voltage of transition from the Ohm law to the
exponential dependence of the current (I) on the voltage (U) and the threshold voltage of transition into the region of negative differential resistance dU/dI = s< 0 linearly depend on the sample thickness. The activation energies of conductivity in low and high electric fields are
determined. It is established that the superlinear portion of the I–V characteristic with dU/dI > 0 is described by the dependence of the type I = I
0 exp(U/U
0) and caused by the electron transitions from the local centers with the energy level E
t = 0.19 eV. 相似文献
17.
Cu0.003Bi0.4Sb1.6Te3 alloys were prepared by using encapsulated melting and hot extrusion (HE). The hot-extruded specimens had the relative average density of 98%. The (00l) planes were preferentially oriented parallel to the extrusion direction, but the specimens showed low crystallographic anisotropy with low orientation factors. The specimens were hot-extruded at 698 K, and they showed excellent mechanical properties with a Vickers hardness of 76 Hv and a bending strength of 59 MPa. However, as the HE temperature increased, the mechanical properties degraded due to grain growth. The hot-extruded specimens showed positive Seebeck coefficients, indicating that the specimens have p-type conduction. These specimens exhibited negative temperature dependences of electrical conductivity, and thus behaved as degenerate semiconductors. The Seebeck coefficient reached the maximum value at 373 K and then decreased with increasing temperature due to intrinsic conduction. Cu-doped specimens exhibited high power factors due to relatively higher electrical conductivities and Seebeck coefficients than those of undoped specimens. A thermal conductivity of 1.00 Wm?1 K?1 was obtained at 373 K for Cu0.003Bi0.4Sb1.6Te3 hot-extruded at 723 K. A maximum dimensionless figure of merit, ZT max = 1.05, and an average dimensionless figure of merit, ZT ave = 0.98, were achieved at 373 K. 相似文献
18.
The results of studying the thermoelectric properties of p-type Bi0.5Sb1.5Te3 alloy samples prepared by melt spinning quenching are presented. The material after melt spinning is shaped as thin ribbons and has a quasi-amorphous structure. The thermoelectric properties (thermoelectric power and electrical resistance) and crystallization processes of as-prepared melt-spun ribbons are studied at 300–800 K for the first time. The stability range of the initial state, the crystallization-onset temperature, and the effect of thermal annealing on the thermoelectric-power factor of the alloy are determined. 相似文献
19.
In (Bi1.9Sb0.1)1 − x
Sn
x
Te3 solid solution with different contents of Sn, the electrical conductivity (σ11) and the Hall (R
123 and R
321), Seebeck (S
11 and S
33), and Nernst-Ettingshausen (Q
123 and Q
321) coefficients have been measured. It is shown that doping with tin strongly modifies temperature dependences of the kinetic
coefficients. The effect of tin on electrical homogeneity of the samples has been studied: with increasing number of Sn atoms
embedded, crystals become more homogeneous. These features indicate the presence of the quasi-local states of Sn in the valence
band of Bi1.9Sb0.1Te3. Within a one-band model, we estimated the effective mass of the density of hole states (m
d
), the energy gap extrapolated to 0 K (E
g0 = 0.20–0.25 eV), the energy of impurity states (E
Sn ≈ 40–45 meV), and the scattering parameter (r ≈ 0.1–0.4). Numerical values of the scattering parameter indicate a mixed mechanism of scattering in the samples under investigation
with dominant scattering at acoustic phonons. With increasing content of tin in the samples, the contribution of impurity
scattering increases. 相似文献
20.
H. Yin M. Christensen B.L. Pedersen E. Nishibori S. Aoyagi B.B. Iversen 《Journal of Electronic Materials》2010,39(9):1957-1959
The thermal stability of the thermoelectric Zn4Sb3 has been investigated by synchrotron power diffraction measurements in the temperature range of 300 K to 625 K in a capillary
sealed under Ar. Data were also collected in air on a 1% Cd-doped sample. Rietveld refinements of the data indicate that a
variety of impurity phases are formed. After heat treatment, more than 85% of the Zn4Sb3 phase remains in the 1% Cd-doped sample heated in air, and 97% remains in the undoped Zn4Sb3 heated in Ar. These stabilities are better than those previously observed in pure samples heated in air. This suggests that
doping, as well as oxygen or oxidation impurities, play important roles in the thermal stability of this compound. 相似文献