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1
Content available remote

Interface Mixing in Fe/Si Multilayers Observed by the In Situ Conductance Measurements

100%
Chomiuk P., Błaszyk M., Szymański B., Luciński T.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
355-356
EN
In this contribution the in situ conductance vs. deposition time dependences of Fe/Si multilayers are analysed. The plot of resistance multiplied by the square of the thickness as a function of iron thickness shows that during the iron deposition initially amorphous-like Fe-Si mixture is formed, next the mixture crystallises, and finally bcc-Fe phase appears. The interface mixing is also manifested by the reduction of the total multilayer thickness measured by small angle X-ray diffraction.
2
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Gain and Dark Current Studies on Planar Photodetectors Made on Annealed GaAs-on-Si

80%
Riesz F., Tuven V. V., Varrio J.
Acta Physica Polonica A
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1995
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vol. 88
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issue 5
889-892
EN
Interdigital, planar photodetectors were fabricated from annealed GaAs/Si heterostructures grown by molecular beam epitaxy using alloyed AuGe/Ni and non-alloyed Cr/Au contacts. The dark current and optical gain of the Cr/Au devices is higher than that of the AuGe/Ni devices. Contact degradation due to annealing and a p-like background doping consistently explains our data. The gain-optical power relationship follows a power law with an exponent close to -1.
3
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Zinc Oxide/Cuprous(I) Oxide-Based Solar Cells Prepared by Electrodeposition

80%
Pławecki M., Rówiński E., Mieszczak Ł.
Acta Physica Polonica A
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2016
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vol. 130
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issue 4
1144-1146
EN
The aim of this research was to fabricate zinc oxide/cuprous(I) oxide-based heterojunction solar cells with the use of electrodeposition methods, and further to investigate their structures and photovoltaic properties. The ZnO and Cu₂O were used as n- and p-type semiconductors, respectively, to fabricate photovoltaic devices based on Ag/ZnO/Cu₂O/Cu(100) heterojunction structures. The crystallite sizes of ZnO and Cu₂O were determined to be 25.4(3) nm and 69.8(6) nm, respectively. It was pointed out that efficiencies of the solar cells can be gradually adjusted, using different thicknesses of Cu₂O layers, to achieve values as high as 2.7%. The standard diode model and high device performance provide new insights into the issue, outlining guidelines for high-performance solar cells and suggesting that a metal-n-type semiconductor-p-type semiconductor nanostructure-crystal layered, sandwiched-type architecture is a promising platform: to boost the efficiency.
4
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Structural and Electrical Properties of Electrodeposited Single Junction of Cuprous (I) Oxide-Copper

80%
Rówiński E., Pławecki M.
Acta Physica Polonica A
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2016
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vol. 130
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issue 4
1141-1143
EN
Cuprous (I) oxide (Cu₂O)-based solar cells were fabricated with the use of the electrodeposition technique at nanometre-scale, and the structural, morphological and electrical properties were investigated. The Cu₂O layers were electrodeposited on crystalline and polycrystalline copper substrates. To complete the Cu₂O/Cu(100) and Cu₂O/Cu interfaces as the solar cells the top electrodes of silver paste were painted on the rear of Cu₂O. The microscopic analysis exhibits uneven surface morphologies of a Cu₂O film with the roughness of 92.5 nm, while the X-ray diffraction analysis reveals that the layers are Cu₂O-type polycrystalline structures with the thickness of 493 nm and the crystallite size of 69.8(6) nm. The theoretical analysis of the current-voltage curve was provided to determine the values of electrical parameters of the most efficient solar cell of Ag/Cu₂O/Cu(100) and clearly indicate presence of two Schottky barriers at interfaces.
5
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Spin Dependent Fano Resonances in a Rashba System with Coulomb Interactions

80%
Stefański P.
Acta Physica Polonica A
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2011
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vol. 119
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issue 5
644-647
EN
The effects of interplay of interference of quantum mechanical electron waves and their mutual Coulomb interactions are investigated in the device composed of interacting quantum dot attached to polarized leads via quantum point contacts with the Rashba interaction. The Zeeman-split dot sub-levels form two interfering channels and as a result spin dependent Fano resonances arise in the conductance through the system. The Coulomb repulsion between the channels modifies the width and shape of the Fano resonances as compared to the non-interacting case. We formulate the Fano expression dependent on the dot's occupancy regulated by the Coulomb interactions.
6
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Content available

Annealing Study of Al/GaSb Contact with the Use of Doppler Broadening Technique

80%
Wang H., Weng H., Ling C., Ye B., Zhou X., Han R.
Acta Physica Polonica A
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2005
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vol. 107
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issue 5
874-879
EN
Using a monoenergetic positron beam, annealing study of the Al/n-GaSb system was performed by monitoring the Doppler broadening of the annihilation radiation as a function of the positron implanting energy. The S-parameter against positron energy data was successfully fitted by a three-layer model (Al/interface/GaSb). The annealing out of the open volume defects in the polycrystalline Al layer was revealed by the decrease in the S-parameter and the increase in the effective diffusion length of the Al layer. For the as-deposited samples, a 5 nm interfacial region with S-parameter larger than those of the Al overlayer and the bulk was identified. After the 400ºC annealing, this interfacial region extends to over 40 nm and its S-parameter dramatically drops. This is possibly due to the new phase formation at the interface. Annealing behaviors of S_B and L_{+,B} of the GaSb bulk showed the annealing out of positron traps (possibly the V_{Ga}-related defect) at 250ºC. However, a further annealing at 400ºC induces the formation of positron traps, which are possibly of another kind of V_{Ga}-related defect and the positron shallow trap GaSb antisite.
7
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Morphology, Optical and AC Electrical Properties of Copper Phthalocyanine Thin Films

80%
Azim-Araghi M., Haji Mirza Mohamadi S., Bisadi Z.
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vol. 125
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issue 1
87-92
EN
AC electrical properties of sandwich devices composed of thermally evaporated thin films of copper phthalocyanine (CuPc) with aluminum and gold electrodes (Al/CuPc/Au) are investigated over frequency (f) range of 10^2 - 10^5 Hz and temperature range of 293-453 K. Morphology of the samples was studied via field emission scanning electron microscope images and X-ray diffraction micrographs. The X-ray diffraction micrograph indicates the configuration of α-CuPc with the (510) plane as the preferred orientation. UV-Vis absorption spectrum was analyzed and the optical band-gap energy of CuPc thin film was determined to be 2.81 ± 0.01 eV. Capacitance increased with increasing temperature especially for f = 10^2 Hz. Loss factor decreased considerably with increasing frequency to a minimum value at about f = 10^4 Hz and increased afterwards. Capacitance is generally independent of frequency for T ≤ 413 K; however it decreases remarkably with increasing frequency for T > 413 K. The conductivity increases quite noticeably with increasing frequency particularly for T ≤ 413 K. The AC electrical characteristics are in good agreement with Goswami and Goswami model. According to our data, at high temperatures, the band theory is applicable in describing the conduction process, whereas hopping mechanism is dominant at low temperatures.
8
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Content available

High Speed Heterostructure Metal-Semiconductor-Metal Photodetectors

80%
Cola A., Nabet B., Chen X., Quaranta F.
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EN
In this work we review the properties of a class of metal-semiconductor-metal photodetectors based on heterojunction structures. Particularly, an AlGaAs/GaAs device is detailed in which the absorption region is in the GaAs layer, and a two-dimensional electron gas is formed at the heterointerface due toδ-doping of the widegap material. This heterostructure metal-semiconductor-metal photodetector also contains an AlGaAs distributed Bragg reflector that forms a resonant cavity for detection at 850 nm. The beneficial effect of the two-dimensional electron gas in the GaAs absorption layer in terms of speed and sensitivity is demonstrated by comparing samples with and without doping in the AlGaAs layer. The design and the physical properties of the grown epitaxial structure are presented, together with the static and dynamic characteristics of the device in time domain. In particular, photocurrent spectra exhibit a 30 nm wide peak at 850 nm, and time response measurements give a bandwidth over 30 GHz. A combination of very low dark current and capacitance, fast response, wavelength selectivity, and compatibility with high electron mobility transistors makes this device suitable for a number of application areas, such as Gigabit and 10 Gigabit Ethernet, wavelength division multiplexing, remote sensing, and medical applications.
9
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In Situ Conductance of Fe/Si and Fe/Ge Multilayers

80%
Chomiuk P., Błaszyk M., Luciński T., Wróblewski M., Susła B.
Acta Physica Polonica A
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2008
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vol. 113
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issue 2
657-662
EN
In this paper we study Fe/Si and Fe/Ge multilayers prepared at room temperature by magnetron sputtering. In situ conductance measurements reveal the formation of interfacial Fe-Si and Fe-Ge mixtures. During the Fe deposition a modification of growth mode is noticed. Deposition of Si (or Ge) onto Fe leads to the reduction of the Fe layer thickness due to interdiffusion, and Fe-Si (or Fe-Ge) structures appear. Above about 1.3 nm of deposited Si (1.5 nm of Ge) nominally pure Si (Ge) starts growing. Surface topography of the Fe/Si multilayers is studied by atomic force microscopy.
10
Content available remote

Electrical Behaviour of Nanostructured Porous Silicon

61%
Azim-Araghi M., Ashrafabadi S., Kanjuri F.
Acta Physica Polonica A
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2012
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vol. 122
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issue 1
170-173
EN
The electrical behaviour of porous silicon layers has been investigated on one side of p-type silicon with various anodization currents, electrolytes, and times. Electron microscopy reveals the evolution of porous silicon layer morphology with variation in anodization time. In this work electrical conductivity of bulk silicon and porous layer which is formed by electrochemical etching is compared due to I-V measurements and calculation of activation energy. We have also studied the dependence of porous silicon conductivity on fabrication conditions. Also the effect of the temperature on conduction of porous silicon at different frequencies is investigated. At last dependence of capacitance on the temperature was probed at 10^2 - 10^5 Hz frequency range.
11
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Content available

Ballistic Electrons in Ferromagnet/Semiconductor Hybrid Structures: From Nanomagnetometry to Spin Injection

61%
Grundler D.
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issue 4-5
529-540
EN
We review our recent experimental and theoretical studies on ferromagnet/semiconductor hybrid structures and discuss the role of ballistic electrons in such systems. We focus in particular on two peculiar features: first, ballistic electrons in semiconductors are shown to be in particular sensitive to local details of an inhomogeneous stray field. We argue that this can preferentially be used for nanomagnetometry. Second, we show theoretically that, in case of the injection of ballistic electrons from a metallic ferromagnet into a semiconductor, a spin-dependent interface resistance arises due to band-structure mismatch that causes spin filtering at the interface. Recent band-structure calculations suggest that for an epitaxial interface a nearly 100% spin-polarized current might be generated in a spin-injection experiment.
12
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Mott-Schottky Analysis of the P3HT:ZnS_{cubic} and P3HT:ZnS_{hexa} Bulk Heterojunction Solar Cells

51%
Abdul Kareem T.
Acta Physica Polonica A
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2016
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vol. 129
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issue 3
409-413
EN
Bulk heterojunction solar cells of sphalerite and wurtzite ZnS incorporated P3HT were fabricated and their Mott-Schottky analysis was performed to find the conduction mechanism of the devices. The analysis shows the formation of a Schottky junction and band unpinning at the P3HT:ZnS-Al contact and it confirms the hole conductivity in the active material.
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