PMCC PMCC

Search tips
Search criteria

Advanced
Results 1-25 (340950)

Clipboard (0)
None

Related Articles

1.  Probing Nucleation Mechanism of Self-Catalyzed InN Nanostructures 
Nanoscale Research Letters  2009;5(1):7-13.
The nucleation and evolution of InN nanowires in a self-catalyzed growth process have been investigated to probe the microscopic growth mechanism of the self-catalysis and a model is proposed for high pressure growth window at ~760 Torr. In the initial stage of the growth, amorphous InNx microparticles of cone shape in liquid phase form with assistance of an InNx wetting layer on the substrate. InN crystallites form inside the cone and serve as the seeds for one-dimensional growth along the favorable [0001] orientation, resulting in single-crystalline InN nanowire bundles protruding out from the cones. An amorphous InNx sheath around the faucet tip serves as the interface between growing InN nanowires and the incoming vapors of indium and nitrogen and supports continuous growth of InN nanowires in a similar way to the oxide sheath in the oxide-assisted growth of other semiconductor nanowires. Other InN 1D nanostructures, such as belts and tubes, can be obtained by varying the InN crystallites nucleation and initiation process.
doi:10.1007/s11671-009-9434-3
PMCID: PMC2894334  PMID: 20652103
Indium nitride; Self-catalyzed; Nanowires; InNx cones; Sheath
2.  Probing Nucleation Mechanism of Self-Catalyzed InN Nanostructures 
Nanoscale Research Letters  2009;5(1):7-13.
The nucleation and evolution of InN nanowires in a self-catalyzed growth process have been investigated to probe the microscopic growth mechanism of the self-catalysis and a model is proposed for high pressure growth window at ~760 Torr. In the initial stage of the growth, amorphous InNx microparticles of cone shape in liquid phase form with assistance of an InNx wetting layer on the substrate. InN crystallites form inside the cone and serve as the seeds for one-dimensional growth along the favorable [0001] orientation, resulting in single-crystalline InN nanowire bundles protruding out from the cones. An amorphous InNx sheath around the faucet tip serves as the interface between growing InN nanowires and the incoming vapors of indium and nitrogen and supports continuous growth of InN nanowires in a similar way to the oxide sheath in the oxide-assisted growth of other semiconductor nanowires. Other InN 1D nanostructures, such as belts and tubes, can be obtained by varying the InN crystallites nucleation and initiation process.
doi:10.1007/s11671-009-9434-3
PMCID: PMC2894334  PMID: 20652103
Indium nitride; Self-catalyzed; Nanowires; InNx cones; Sheath
3.  Transport and infrared photoresponse properties of InN nanorods/Si heterojunction 
Nanoscale Research Letters  2011;6(1):609.
The present work explores the electrical transport and infrared (IR) photoresponse properties of InN nanorods (NRs)/n-Si heterojunction grown by plasma-assisted molecular beam epitaxy. Single-crystalline wurtzite structure of InN NRs is verified by the X-ray diffraction and transmission electron microscopy. Raman measurements show that these wurtzite InN NRs have sharp peaks E2(high) at 490.2 cm-1 and A1(LO) at 591 cm-1. The current transport mechanism of the NRs is limited by three types of mechanisms depending on applied bias voltages. The electrical transport properties of the device were studied in the range of 80 to 450 K. The faster rise and decay time indicate that the InN NRs/n-Si heterojunction is highly sensitive to IR light.
doi:10.1186/1556-276X-6-609
PMCID: PMC3256238  PMID: 22122843
4.  Valence band offset of wurtzite InN/SrTiO3 heterojunction measured by x-ray photoelectron spectroscopy 
Nanoscale Research Letters  2011;6(1):193.
The valence band offset (VBO) of wurtzite indium nitride/strontium titanate (InN/SrTiO3) heterojunction has been directly measured by x-ray photoelectron spectroscopy. The VBO is determined to be 1.26 ± 0.23 eV and the conduction band offset is deduced to be 1.30 ± 0.23 eV, indicating the heterojunction has a type-I band alignment. The accurate determination of the valence and conduction band offsets paves a way to the applications of integrating InN with the functional oxide SrTiO3.
doi:10.1186/1556-276X-6-193
PMCID: PMC3211249  PMID: 21711731
5.  Field-effect transistors based on cubic indium nitride 
Scientific Reports  2014;4:3951.
Although the demand for high-speed telecommunications has increased in recent years, the performance of transistors fabricated with traditional semiconductors such as silicon, gallium arsenide, and gallium nitride have reached their physical performance limits. Therefore, new materials with high carrier velocities should be sought for the fabrication of next-generation, ultra-high-speed transistors. Indium nitride (InN) has attracted much attention for this purpose because of its high electron drift velocity under a high electric field. Thick InN films have been applied to the fabrication of field-effect transistors (FETs), but the performance of the thick InN transistors was discouraging, with no clear linear-saturation output characteristics and poor on/off current ratios. Here, we report the epitaxial deposition of ultrathin cubic InN on insulating oxide yttria-stabilized zirconia substrates and the first demonstration of ultrathin-InN-based FETs. The devices exhibit high on/off ratios and low off-current densities because of the high quality top and bottom interfaces between the ultrathin cubic InN and oxide insulators. This first demonstration of FETs using a ultrathin cubic indium nitride semiconductor will thus pave the way for the development of next-generation high-speed electronics.
doi:10.1038/srep03951
PMCID: PMC3912472  PMID: 24492240
6.  Oxygen Absorption in Free-Standing Porous Silicon: A Structural, Optical and Kinetic Analysis 
Nanoscale Research Letters  2010;5(4):686-691.
Porous silicon (PSi) is a nanostructured material possessing a huge surface area per unit volume. In consequence, the adsorption and diffusion of oxygen in PSi are particularly important phenomena and frequently cause significant changes in its properties. In this paper, we study the thermal oxidation of p+-type free-standing PSi fabricated by anodic electrochemical etching. These free-standing samples were characterized by nitrogen adsorption, thermogravimetry, atomic force microscopy and powder X-ray diffraction. The results show a structural phase transition from crystalline silicon to a combination of cristobalite and quartz, passing through amorphous silicon and amorphous silicon-oxide structures, when the thermal oxidation temperature increases from 400 to 900 °C. Moreover, we observe some evidence of a sinterization at 400 °C and an optimal oxygen-absorption temperature about 700 °C. Finally, the UV/Visible spectrophotometry reveals a red and a blue shift of the optical transmittance spectra for samples with oxidation temperatures lower and higher than 700 °C, respectively.
doi:10.1007/s11671-010-9532-2
PMCID: PMC2893869  PMID: 20672128
Porous silicon; Thermal oxidation; Kinetic analysis; Structural transition; Optical properties
7.  Oxygen Absorption in Free-Standing Porous Silicon: A Structural, Optical and Kinetic Analysis 
Nanoscale Research Letters  2010;5(4):686-691.
Porous silicon (PSi) is a nanostructured material possessing a huge surface area per unit volume. In consequence, the adsorption and diffusion of oxygen in PSi are particularly important phenomena and frequently cause significant changes in its properties. In this paper, we study the thermal oxidation of p+-type free-standing PSi fabricated by anodic electrochemical etching. These free-standing samples were characterized by nitrogen adsorption, thermogravimetry, atomic force microscopy and powder X-ray diffraction. The results show a structural phase transition from crystalline silicon to a combination of cristobalite and quartz, passing through amorphous silicon and amorphous silicon-oxide structures, when the thermal oxidation temperature increases from 400 to 900 °C. Moreover, we observe some evidence of a sinterization at 400 °C and an optimal oxygen-absorption temperature about 700 °C. Finally, the UV/Visible spectrophotometry reveals a red and a blue shift of the optical transmittance spectra for samples with oxidation temperatures lower and higher than 700 °C, respectively.
doi:10.1007/s11671-010-9532-2
PMCID: PMC2893869  PMID: 20672128
Porous silicon; Thermal oxidation; Kinetic analysis; Structural transition; Optical properties
8.  Study of InN epitaxial films and nanorods grown on GaN template by RF-MOMBE 
Nanoscale Research Letters  2012;7(1):468.
This paper reports on high-quality InN materials prepared on a GaN template using radio-frequency metalorganic molecular beam epitaxy. We also discuss the structural and electro-optical properties of InN nanorods/films. The X-ray diffraction peaks of InN(0002) and InN(0004) were identified from their spectra, indicating that the (0001)-oriented hexagonal InN was epitaxially grown on the GaN template. Scanning electron microscopic images of the surface morphology revealed a two-dimensional growth at a rate of approximately 0.85 μm/h. Cross-sectional transmission electron microscopy images identified a sharp InN/GaN interface and a clear epitaxial orientation relationship of [0001]InN // [0001]GaN and ( 2¯110)InN // ( 2¯110)GaN. The optical properties of wurtzite InN nanorods were determined according to the photoluminescence, revealing a band gap of 0.77 eV.
doi:10.1186/1556-276X-7-468
PMCID: PMC3492109  PMID: 22908859
RF-MOMBE; InN; nanorods
9.  Epitaxial Catalyst-Free Growth of InN Nanorods on c-Plane Sapphire 
Nanoscale Research Letters  2009;4(6):532-537.
We report observation of catalyst-free hydride vapor phase epitaxy growth of InN nanorods. Characterization of the nanorods with transmission electron microscopy, and X-ray diffraction show that the nanorods are stoichiometric 2H–InN single crystals growing in the [0001] orientation. The InN rods are uniform, showing very little variation in both diameter and length. Surprisingly, the rods show clear epitaxial relations with the c-plane sapphire substrate, despite about 29% of lattice mismatch. Comparing catalyst-free with Ni-catalyzed growth, the only difference observed is in the density of nucleation sites, suggesting that Ni does not work like the typical vapor–liquid–solid catalyst, but rather functions as a nucleation promoter by catalyzing the decomposition of ammonia. No conclusive photoluminescence was observed from single nanorods, while integrating over a large area showed weak wide emissions centered at 0.78 and at 1.9 eV.
doi:10.1007/s11671-009-9276-z
PMCID: PMC2893868  PMID: 20596436
InN; Nanorods; Nanowires; Epitaxial growth; Sapphire; Catalyst-free; Ni
10.  Epitaxial Catalyst-Free Growth of InN Nanorods onc-Plane Sapphire 
Nanoscale Research Letters  2009;4(6):532-537.
We report observation of catalyst-free hydride vapor phase epitaxy growth of InN nanorods. Characterization of the nanorods with transmission electron microscopy, and X-ray diffraction show that the nanorods are stoichiometric 2H–InN single crystals growing in the [0001] orientation. The InN rods are uniform, showing very little variation in both diameter and length. Surprisingly, the rods show clear epitaxial relations with thec-plane sapphire substrate, despite about 29% of lattice mismatch. Comparing catalyst-free with Ni-catalyzed growth, the only difference observed is in the density of nucleation sites, suggesting that Ni does not work like the typical vapor–liquid–solid catalyst, but rather functions as a nucleation promoter by catalyzing the decomposition of ammonia. No conclusive photoluminescence was observed from single nanorods, while integrating over a large area showed weak wide emissions centered at 0.78 and at 1.9 eV.
doi:10.1007/s11671-009-9276-z
PMCID: PMC2893868  PMID: 20596436
InN; Nanorods; Nanowires; Epitaxial growth; Sapphire; Catalyst-free; Ni
11.  Determination of InN/Diamond Heterojunction Band Offset by X-ray Photoelectron Spectroscopy 
Shi, K | Li, DB | Song, HP | Guo, Y | Wang, J | Xu, XQ | Liu, JM | Yang, AL | Wei, HY | Zhang, B | Yang, SY | Liu, XL | Zhu, QS | Wang, ZG
Diamond is not only a free standing highly transparent window but also a promising carrier confinement layer for InN based devices, yet little is known of the band offsets in InN/diamond system. X-ray photoelectron spectroscopy was used to measure the energy discontinuity in the valence band offset (VBO) of InN/diamond heterostructure. The value of VBO was determined to be 0.39 ± 0.08 eV and a type-I heterojunction with a conduction band offset (CBO) of 4.42 ± 0.08 eV was obtained. The accurate determination of VBO and CBO is important for the application of III-N alloys based electronic devices.
doi:10.1007/s11671-010-9796-6
PMCID: PMC3212014
Valence band offset; InN/diamond heterojunction; X-ray photoelectron spectroscopy; Conduction band offset
12.  Structural, electronic and vibrational properties of InN under high pressure 
Physica. B, Condensed Matter  2012;407(6):1008-1013.
The structural, electronic and vibrational properties of InN under pressures up to 20 GPa have been investigated using the pseudo-potential plane wave method (PP-PW). The generalized-gradient approximation (GGA) in the frame of density functional theory (DFT) approach has been adopted. It is found that the transition from wurtzite (B4) to rocksalt (B1) phase occurs at a pressure of approximately 12.7 GPa. In addition, a change from a direct to an indirect band gap is observed. The mechanism of these changes is discussed. The phonon frequencies and densities of states (DOS) are derived using the linear response approach and density functional perturbation theory (DFPT). The properties of phonons are described by the harmonic approximation method. Our results show that phonons play an important role in the mechanism of phase transition and in the instability of B4 (wurtzite) just before the pressure of transition. At zero pressure our data agree well with recently reported experimental results.
doi:10.1016/j.physb.2011.12.129
PMCID: PMC3299643  PMID: 22485065
Electronic structure; High pressure; Phase transition
13.  The InN epitaxy via controlling In bilayer 
The method of In bilayer pre-deposition and penetrated nitridation had been proposed, which had been proven to have many advantages theoretically. To study the growth behavior of this method experimentally, various pulse times of trimethylindium supply were used to get the optimal indium bilayer controlling by metalorganic vapour phase epitaxy. The results revealed that the InN film quality became better as the thickness of the top indium atomic layers was close to bilayer. A following tuning of nitridation process enhanced the quality of InN film further, which means that a moderate, stable, and slow nitridation process by NH3 flow also plays the key role in growing better-quality InN film. Meanwhile, the biaxial strain of InN film was gradually relaxing when the flatness was increasingly improved.
doi:10.1186/1556-276X-9-5
PMCID: PMC3895708  PMID: 24393422
InN epitaxy; MOVPE; Bilayer control; Penetrated nitridation
14.  InN Based Water Condensation Sensors on Glass and Flexible Plastic Substrates 
Sensors (Basel, Switzerland)  2013;13(12):16940-16949.
In this paper, we report the realization and characterization of a condensation sensor based on indium nitride (InN) layers deposited by magnetron sputtering on glass and flexible plastic substrates, having fast response and using potentially low cost fabrication technology. The InN devices work as open gate thin film sensitive transistors. Condensed water droplets, formed on the open gate region of the sensors, deplete the electron accumulation layer on the surface of InN film, thus decreasing the current of the sensor. The current increases back to its initial value when water droplets evaporate from the exposed InN film surface. The response time is as low as 2 s.
doi:10.3390/s131216940
PMCID: PMC3892822  PMID: 24322566
III-nitride; indium nitride; condensation sensor; surface accumulation layer
15.  A Sub-ppm Acetone Gas Sensor for Diabetes Detection Using 10 nm Thick Ultrathin InN FETs 
Sensors (Basel, Switzerland)  2012;12(6):7157-7168.
An indium nitride (InN) gas sensor of 10 nm in thickness has achieved detection limit of 0.4 ppm acetone. The sensor has a size of 1 mm by 2.5 mm, while its sensing area is 0.25 mm by 2 mm. Detection of such a low acetone concentration in exhaled breath could enable early diagnosis of diabetes for portable physiological applications. The ultrathin InN epilayer extensively enhances sensing sensitivity due to its strong electron accumulation on roughly 5–10 nm deep layers from the surface. Platinum as catalyst can increase output current signals by 2.5-fold (94 vs. 37.5 μA) as well as reduce response time by 8.4-fold (150 vs. 1,260 s) in comparison with bare InN. More, the effect of 3% oxygen consumption due to breath inhalation and exhalation on 2.4 ppm acetone gas detection was investigated, indicating that such an acetone concentration can be analyzed in air.
doi:10.3390/s120607157
PMCID: PMC3435971  PMID: 22969342
indium nitride (InN); acetone; gas sensor; diabetic; platinum (Pt)
16.  Nonstoichiometric Titanium Oxides via Pulsed Laser Ablation in Water 
Nanoscale Research Letters  2010;5(6):972-985.
Titanium oxide compounds TiO, Ti2O3, and TiO2 with a considerable extent of nonstoichiometry were fabricated by pulsed laser ablation in water and characterized by X-ray/electron diffraction, X-ray photoelectron spectroscopy and electron energy loss spectroscopy. The titanium oxides were found to occur as nanoparticle aggregates with a predominant 3+ charge and amorphous microtubes when fabricated under an average power density of ca. 1 × 108 W/cm2 and 1011 W/cm2, respectively followed by dwelling in water. The crystalline colloidal particles have a relatively high content of Ti2+ and hence a lower minimum band gap of 3.4 eV in comparison with 5.2 eV for the amorphous state. The protonation on both crystalline and amorphous phase caused defects, mainly titanium rather than oxygen vacancies and charge and/or volume-compensating defects. The hydrophilic nature and presumably varied extent of undercoordination at the free surface of the amorphous lamellae accounts for their rolling as tubes at water/air and water/glass interfaces. The nonstoichiometric titania thus fabricated have potential optoelectronic and catalytic applications in UV–visible range and shed light on the Ti charge and phase behavior of titania-water binary in natural shock occurrence.
doi:10.1007/s11671-010-9591-4
PMCID: PMC2894151  PMID: 20672115
Titanium oxide; Nonstoichiometry; Structure; Optical property; Pulsed laser ablation in water; TEM
17.  Nonstoichiometric Titanium Oxides via Pulsed Laser Ablation in Water 
Nanoscale Research Letters  2010;5(6):972-985.
Titanium oxide compounds TiO,Ti2O3, and TiO2 with a considerable extent of nonstoichiometry were fabricated by pulsed laser ablation in water and characterized by X-ray/electron diffraction, X-ray photoelectron spectroscopy and electron energy loss spectroscopy. The titanium oxides were found to occur as nanoparticle aggregates with a predominant 3+ charge and amorphous microtubes when fabricated under an average power density of ca. 1 × 108W/cm2 and 1011W/cm2, respectively followed by dwelling in water. The crystalline colloidal particles have a relatively high content of Ti2+ and hence a lower minimum band gap of 3.4 eV in comparison with 5.2 eV for the amorphous state. The protonation on both crystalline and amorphous phase caused defects, mainly titanium rather than oxygen vacancies and charge and/or volume-compensating defects. The hydrophilic nature and presumably varied extent of undercoordination at the free surface of the amorphous lamellae accounts for their rolling as tubes at water/air and water/glass interfaces. The nonstoichiometric titania thus fabricated have potential optoelectronic and catalytic applications in UV–visible range and shed light on the Ti charge and phase behavior of titania-water binary in natural shock occurrence.
doi:10.1007/s11671-010-9591-4
PMCID: PMC2894151  PMID: 20672115
Titanium oxide; Nonstoichiometry; Structure; Optical property; Pulsed laser ablation in water; TEM
18.  Effects of crystallization and dopant concentration on the emission behavior of TiO2:Eu nanophosphors 
Uniform, spherical-shaped TiO2:Eu nanoparticles with different doping concentrations have been synthesized through controlled hydrolysis of titanium tetrabutoxide under appropriate pH and temperature in the presence of EuCl3·6H2O. Through air annealing at 500°C for 2 h, the amorphous, as-grown nanoparticles could be converted to a pure anatase phase. The morphology, structural, and optical properties of the annealed nanostructures were studied using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy [EDS], and UV-Visible diffuse reflectance spectroscopy techniques. Optoelectronic behaviors of the nanostructures were studied using micro-Raman and photoluminescence [PL] spectroscopies at room temperature. EDS results confirmed a systematic increase of Eu content in the as-prepared samples with the increase of nominal europium content in the reaction solution. With the increasing dopant concentration, crystallinity and crystallite size of the titania particles decreased gradually. Incorporation of europium in the titania particles induced a structural deformation and a blueshift of their absorption edge. While the room-temperature PL emission of the as-grown samples is dominated by the 5D0 - 7Fj transition of Eu+3 ions, the emission intensity reduced drastically after thermal annealing due to outwards segregation of dopant ions.
doi:10.1186/1556-276X-7-1
PMCID: PMC3260088  PMID: 22214494
titania nanoparticles; europium doping; optical properties; photoluminescence
19.  Dye–Sensitized Nanostructured Crystalline Mesoporous Tin-doped Indium Oxide Films with Tunable Thickness for Photoelectrochemical Applications 
A simple route towards nanostructured mesoporous Indium–Tin Oxide (templated nano–ITO) electrodes exhibiting both high conductivities and optimized bicontinuous pore–solid network is reported. The ITO films are first produced as an X–ray–amorphous, high surface area material, by adapting recently established template–directed sol–gel methods using Sn(IV) and In(III) salts. Carefully controlled temperature/atmosphere treatments convert the as–synthesized ITO films into nano-crystalline coatings with the cubic bixbyite structure. Specially, a multi-layered synthesis was successfully undertaken for tuning the film thickness. In order to evaluate the performances of templated nano–ITO as an electrode substrate for photoelectrochemical applications, photoelectrodes were prepared by covalent grafting of a redox–active dye, the complex [Ru(bpy)2(4,4′-(CH2PO3H2)2-bpy)]Cl2 1 (bpy=bipyridine). Surface coverage was shown to increase with the film thickness, from 0.7 × 10−9 mol.cm−2 (one layer, 45 nm) to 3.5 × 10−9 mol.cm−2 (ten layers, 470 nm), the latter value being ~ 100 times larger than that for commercially available planar ITO. In the presence of an electron mediator, photocurrents up to 50 μA.cm−2 have been measured under visible light irradiation, demonstrating the potential of this new templated nano-ITO preparation for the construction of efficient photoelectrochemical devices.
doi:10.1039/C3TA10728K
PMCID: PMC3880857
ITO; Mesoporous; Sol-gel Process; Multi-layered; Ruthenium dye; Photocurrents
20.  Quantification of Surface Amorphous Content Using Dispersive Surface Energy: the Concept of Effective Amorphous Surface Area 
AAPS PharmSciTech  2011;12(3):887-892.
We investigate the use of dispersive surface energy in quantifying surface amorphous content, and the concept of effective amorphous surface area is introduced. An equation is introduced employing the linear combination of surface area normalized square root dispersive surface energy terms. This equation is effective in generating calibration curves when crystalline and amorphous references are used. Inverse gas chromatography is used to generate dispersive surface energy values. Two systems are investigated, and in both cases surface energy data collected for physical mixture samples comprised of amorphous and crystalline references fits the predicted response with good accuracy. Surface amorphous content of processed lactose samples is quantified using the calibration curve, and interpreted within the context of effective amorphous surface area. Data for bulk amorphous content is also utilized to generate a thorough picture of how disorder is distributed throughout the particle. An approach to quantifying surface amorphous content using dispersive surface energy is presented. Quantification is achieved by equating results to an effective amorphous surface area based on reference crystalline, and amorphous materials.
doi:10.1208/s12249-011-9655-5
PMCID: PMC3167268  PMID: 21725707
amorphous; dispersive surface energy; IGC; quantification
21.  Low Temperature Growth of In2O3 and InN Nanocrystals on Si(111) via Chemical Vapour Deposition Based on the Sublimation of NH4Cl in In 
Nanoscale Research Letters  2009;4(6):491-497.
Indium oxide (In2O3) nanocrystals (NCs) have been obtained via atmospheric pressure, chemical vapour deposition (APCVD) on Si(111) via the direct oxidation of In with Ar:10% O2 at 1000 °C but also at temperatures as low as 500 °C by the sublimation of ammonium chloride (NH4Cl) which is incorporated into the In under a gas flow of nitrogen (N2). Similarly InN NCs have also been obtained using sublimation of NH4Cl in a gas flow of NH3. During oxidation of In under a flow of O2 the transfer of In into the gas stream is inhibited by the formation of In2O3 around the In powder which breaks up only at high temperatures, i.e. T > 900 °C, thereby releasing In into the gas stream which can then react with O2 leading to a high yield formation of isolated 500 nm In2O3 octahedrons but also chains of these nanostructures. No such NCs were obtained by direct oxidation for TG < 900 °C. The incorporation of NH4Cl in the In leads to the sublimation of NH4Cl into NH3 and HCl at around 338 °C which in turn produces an efficient dispersion and transfer of the whole In into the gas stream of N2 where it reacts with HCl forming primarily InCl. The latter adsorbs onto the Si(111) where it reacts with H2O and O2 leading to the formation of In2O3 nanopyramids on Si(111). The rest of the InCl is carried downstream, where it solidifies at lower temperatures, and rapidly breaks down into metallic In upon exposure to H2O in the air. Upon carrying out the reaction of In with NH4Cl at 600 °C under NH3 as opposed to N2, we obtain InN nanoparticles on Si(111) with an average diameter of 300 nm.
doi:10.1007/s11671-009-9266-1
PMCID: PMC2894321  PMID: 20596336
Indium oxide; Indium nitride; Nanocrystals; Low temperature; Chemical vapour deposition
22.  Low Temperature Growth of In2O3and InN Nanocrystals on Si(111) via Chemical Vapour Deposition Based on the Sublimation of NH4Cl in In 
Nanoscale Research Letters  2009;4(6):491-497.
Indium oxide (In2O3) nanocrystals (NCs) have been obtained via atmospheric pressure, chemical vapour deposition (APCVD) on Si(111) via the direct oxidation of In with Ar:10% O2at 1000 °C but also at temperatures as low as 500 °C by the sublimation of ammonium chloride (NH4Cl) which is incorporated into the In under a gas flow of nitrogen (N2). Similarly InN NCs have also been obtained using sublimation of NH4Cl in a gas flow of NH3. During oxidation of In under a flow of O2the transfer of In into the gas stream is inhibited by the formation of In2O3around the In powder which breaks up only at high temperatures, i.e.T > 900 °C, thereby releasing In into the gas stream which can then react with O2leading to a high yield formation of isolated 500 nm In2O3octahedrons but also chains of these nanostructures. No such NCs were obtained by direct oxidation forTG < 900 °C. The incorporation of NH4Cl in the In leads to the sublimation of NH4Cl into NH3and HCl at around 338 °C which in turn produces an efficient dispersion and transfer of the whole In into the gas stream of N2where it reacts with HCl forming primarily InCl. The latter adsorbs onto the Si(111) where it reacts with H2O and O2leading to the formation of In2O3nanopyramids on Si(111). The rest of the InCl is carried downstream, where it solidifies at lower temperatures, and rapidly breaks down into metallic In upon exposure to H2O in the air. Upon carrying out the reaction of In with NH4Cl at 600 °C under NH3as opposed to N2, we obtain InN nanoparticles on Si(111) with an average diameter of 300 nm.
doi:10.1007/s11671-009-9266-1
PMCID: PMC2894321  PMID: 20596336
Indium oxide; Indium nitride; Nanocrystals; Low temperature; Chemical vapour deposition
23.  Oxidation of Manganese and Formation of Mn3O4 (Hausmannite) by Spore Coats of a Marine Bacillus sp 
Isolated spore coats of a marine Bacillus species were incubated in 25 mM MnCl2 at pH 7.5. Manganese precipitates, formed on the coat surfaces, were analyzed by transmission electron microscopy, electron diffraction, and energy-dispersive X-ray spectroscopy. Initially, an amorphous manganese oxide was observed on the coats which recrystallized to hausmannite after prolonged incubation in the MnCl2 solution. The spore coats catalyze the oxidation of Mn(II) and have no structural influence on the final mineral phase precipitated.
Images
PMCID: PMC202818  PMID: 16347723
24.  The role of the surfaces in the photon absorption in Ge nanoclusters embedded in silica 
Nanoscale Research Letters  2011;6(1):135.
The usage of semiconductor nanostructures is highly promising for boosting the energy conversion efficiency in photovoltaics technology, but still some of the underlying mechanisms are not well understood at the nanoscale length. Ge quantum dots (QDs) should have a larger absorption and a more efficient quantum confinement effect than Si ones, thus they are good candidate for third-generation solar cells. In this work, Ge QDs embedded in silica matrix have been synthesized through magnetron sputtering deposition and annealing up to 800°C. The thermal evolution of the QD size (2 to 10 nm) has been followed by transmission electron microscopy and X-ray diffraction techniques, evidencing an Ostwald ripening mechanism with a concomitant amorphous-crystalline transition. The optical absorption of Ge nanoclusters has been measured by spectrophotometry analyses, evidencing an optical bandgap of 1.6 eV, unexpectedly independent of the QDs size or of the solid phase (amorphous or crystalline). A simple modeling, based on the Tauc law, shows that the photon absorption has a much larger extent in smaller Ge QDs, being related to the surface extent rather than to the volume. These data are presented and discussed also considering the outcomes for application of Ge nanostructures in photovoltaics.
PACS: 81.07.Ta; 78.67.Hc; 68.65.-k
doi:10.1186/1556-276X-6-135
PMCID: PMC3211182  PMID: 21711648
25.  Silicon and Phosphorus Linkage with Iron via Oxygen in the Amorphous Matrix of Gallionella ferruginea Stalks 
Bacterial species belonging to the genus Gallionella are Fe-oxidizing bacteria that produce uniquely twisted extracellular stalks consisting of iron-oxide-encrusted inorganic/organic fibers in aquatic environments. This paper describes the degree of crystallinity of Gallionella stalks and the chemical linkages of constituent elements in the stalk fibers. Transmission electron microscopy revealed that the matrix of the fiber edge consisted of an assembly of primary particles of approximately 3 nm in diameter. Scanning transmission electron microscopy revealed the rough granular surfaces of the fibers, which reflect the disordered assembly of the primary particles, indicating a high porosity and large specific surface area of the fibers. This may provide the surface with broader reactive properties. X-ray diffractometry, selected-area electron diffraction, and high-resolution transmission electron microscopy together showed that the primary particles had an amorphous structure. Furthermore, energy-dispersive X-ray analysis and Fourier transform infrared spectroscopy detected the bands characteristic of the vibrational modes assigned to O-H, Fe-O-H, P-O-H, Si-O-H, Si-O-Fe, and P-O-Fe bonds in the stalks, suggesting that the minor constituent elements P and Si could affect the degree of crystallinity of the fibers by linking with Fe via O. This knowledge about the mutual associations of these elements provides deeper insights into the unique inorganic/organic hybrid structure of the stalks.
doi:10.1128/AEM.05913-11
PMCID: PMC3255642  PMID: 22020519

Results 1-25 (340950)