Classification of electrical properties of porous silicon

Zimin, S. P.

doi:10.1134/1.1187985

Cited by 32 publications

(18 citation statements)

References 24 publications

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“…In such open surface layers electric conductivity is considered to occur by jumps of charge carriers between crystallites. 20 The character of changing the surface potential for the Pt/PS nanocomposites at P > 40% (see curves 3 and 4) differs from the dependences obtained for PS in the ab sence of Pt (see curves 1 and 2). First, with the introduc tion of Pt nanoparticles into the nanoporous PS matrix the value of U s does not increase as in the case of nonpo rous silicon, but decreases considerably.…”

Section: Resultsmentioning

confidence: 48%

Formation of nanocomposite platinum catalysts on porous silicon

et al. 2011

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Platinum nanoparticles supported on porous silicon were synthesized by radiation chemi cal reduction in solutions of reverse micelles. The Pt nanoparticles obtained are electron deficient. The degree of porosity, conductivity type, pore geometry of the silicon matrix, and precursor parameters affect the size, shape, and charge state of the platinum catalysts.Platinum and platinum based composites are consid ered to be the best catalysts of oxygen reduction reactions (ORR) and hydrogen oxidation reactions (HOR) that occur in electrochemical power generators. It was shown in a series of our works 1-4 and other publications 5-8 that nanoparticles of platinum metals and silver supported on porous silicon (PS) and carbon nanotubes are efficient electrocatalysts for fuel cells.Synthesis of metal nanoparticles in solutions of reverse micelles followed by their subsequent adsorption on po rous supports is a promising method for nanoelectrocata lyst formation. 2-4 Reverse micelles are spherical micro droplets of water (pools) stabilized by surfactants (Surf) in an organic solvent. The molar ratio ω 0 = [H 2 O]/[Surf] defined as the solubilization coefficient determines the size of formed metal nanoparticles during the reduction of their ions in water pools. An increase in this ratio favors the formation of larger nanoparticles.There are few published data describing how the elec trocatalytic activity of nanoparticles deposited on the PS surface is influenced by their physicochemical proper ties. 2-6 Therefore, it is of interest to reveal the character of the metal-PS interaction, morphology of supported particles, charge state of the surface, and possibility of formation of new phases and active sites. Information of this kind makes it possible to better understand specific features of the mechanism of electrocatalytic reactions.The formation of catalytic composites involving Pt nanoparticles can result in the appearance of electron deficient Pt δ+ atoms and the electron density redistribu tion at the Pt/semiconductor interface. In addition, chemi sorption of metal nanoparticles on the support will lead, probably, to the formation of chemical compounds be tween the catalyst and supporting matrix. 9,10 On the one hand, it is considered 11 that the adhesion of Pt nanoparti cles on the silicon support is weak because of the low surface energy of interaction between Pt and Si. On the other hand, it is elucidated that new crystalline phases based on Pt, Re, Ru, and Mo are formed 12,13 during the formation of supported metal catalysts with high degree of dispersity. The high electrocatalytic activity of the nano catalyst Pt 3 Sn was shown 14 in the reaction of EtOH oxi dation. Surface intermetallic compounds Pt 3 Co, Pt 3 CoCr, and Pt x Ni are active in the ORR. 15, 16 To solve many controversial questions about the inter action of metal particles with the support, it is important to know the state of these particles on the surface.Measurements of surface potential are usually used to determine the sign of charge of adsorbed ca...

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Section: Resultsmentioning

confidence: 48%

Formation of nanocomposite platinum catalysts on porous silicon

et al. 2011

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“…This can be explained by the depletion of the n + layer in donor impurity atoms dur ing electrochemical etching. According to [4], the most probable reason for the formation of depleted regions is a transition of impurity atoms into an elec trically inactive state due to the implantation of hydro gen into the crystal lattice of silicon. During electro chemical etching, hydrogen can penetrate from the electrolyte to the crystalline por Si matrix through the pore walls, leading to electric passivation of impurity atoms and forming depleted region around each pore.…”

Section: Peculiarities Of the Capacitance-voltage Characteristic Of Amentioning

confidence: 99%

“…During electro chemical etching, hydrogen can penetrate from the electrolyte to the crystalline por Si matrix through the pore walls, leading to electric passivation of impurity atoms and forming depleted region around each pore. The depleted regions can propagate deep into the bulk of the silicon matrix due to a large diffusion coefficient of hydrogen [4,5].…”

Section: Peculiarities Of the Capacitance-voltage Characteristic Of Amentioning

confidence: 99%

“…Effective thickness d eff of the insulator layer of the structure under investigation was estimated from the value of capacitance C i using the relation derived in [3]: (4) The calculated value of d eff amounted to 0.03 μm. As noted above, the existence of the local peak on the C-V curve (see figure) at U = 0 V is associated with the influence of surface states with deep energy levels.…”

Section: Peculiarities Of the Capacitance-voltage Characteristic Of Amentioning

confidence: 99%

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Peculiarities of the capacitance-voltage characteristic of a photoelectric solar energy convertor based on a silicon p-n junction with a porous silicon antireflection coating

Tregulov

2014

Tech. Phys.

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The application of thin porous silicon (por Si) films as an antireflection coating of the frontal surface of traditional photoelectric convertors (PECs) of solar energy was considered by many authors. It has been shown convincingly that the application of por Si makes it possible to increase the efficiency of solar energy conversion. At the same time, the electrophys ical properties of such PECs have not been studied comprehensively.In this communication, we report on the results of analysis of a high frequency capacitance-voltage (C-V) characteristic of a silicon PEC based on the n + -p junction with a thin por Si film on the n + surface.The structure under investigation is based on the n + -p junction formed by diffusion of phosphorus. The substrate was a silicon single crystal of solar cell qual ity with the p type conductivity, with the (100) orien tation of the surface, and a resistivity of 1 Ω cm. The depth of the n + -p junction was 0.5 μm. The por Si film was grown on the surface of the n + layer by electro chemical anode etching. We investigated a PEC with a 0.4 μm thick por Si film. As shown in our previous pub lication [1], such a thickness of the por Si layer is optimal from the standpoint of the PEC efficiency. Indium con tacts were formed for measurements in the p region of the structure and on the por Si surface.The C-V characteristics were measured by an E7 20 immitance meter for a test signal frequency of 1 MHz at a temperature of 300 K. We tested a batch of ten identical samples with almost identical C-V charac teristics. A typical high frequency C-V curve for the tested batch of samples is shown in the figure. The polarity of a constant bias voltage U applied to the structure is determined by the sign of the voltage at a contact with por Si.The characteristic shown in the figure differs from that for an n + -p diode (initial structure) for which the capacitance minimum must be observed in the region of positive bias voltages.The resultant C-V curve (see figure) is typical of the metal-insulator-semiconductor (MIS) structure based on a semiconductor with n type conductivity. The regime of accumulation of the majority charge carriers is observed in the region of positive voltages. The depletion also begins for high positive voltages (see figure). For a negative bias voltage, deep depletion takes place. The local peak near U = 0 V is associated with the effect of surface states [3]. The voltage of pla nar regions is strongly shifted to the range of positive values, which can be explained by the effect of a nega tive charge in the insulator layer [3].Abstract-Experimental results on the high frequency capacitance-voltage characteristic of a photoelectric solar energy converter based on the n + -p junction with a thin porous silicon film on the frontal surface are considered. It is shown that the capacitance-voltage characteristic is determined by the surface metal-insu lator-semiconductor (MIS) structure formed as a result of growing of a porous silicon layer by electrochem ical anode etching. The ...

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“…According to the quantum confinement model, a heterostructure can be formed between the silicon surface and porous silicon because the latter one has a higher energy bandgap (1.8-2.2 eV) than that of the crystalline silicon [4]. It has recently reported p-n junction devices with metal/porous silicon/p-type silicon (m/PS/p-Si) contact structure which shows the possibility for developing porous silicon-based electronic devices [5,6]. It shows that rectification behavior observed for the I-V characteristics in these devices has been interpreted in terms of the existence of a Schottky barrier between the metal and porous silicon interface [7,8].…”

Section: Introductionmentioning

confidence: 98%

Specific contact resistance and carrier tunneling properties of the silver metal/porous silicon/p-Si ohmic contact structure

Vinod

2009

Journal of Alloys and Compounds

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Classification of electrical properties of porous silicon

Cited by 32 publications

References 24 publications

Formation of nanocomposite platinum catalysts on porous silicon

Formation of nanocomposite platinum catalysts on porous silicon

Peculiarities of the capacitance-voltage characteristic of a photoelectric solar energy convertor based on a silicon p-n junction with a porous silicon antireflection coating

Specific contact resistance and carrier tunneling properties of the silver metal/porous silicon/p-Si ohmic contact structure

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