InP Nanoparticles Research Articles

An Analogous Solution‐Liquid‐Solid (ASLS) Growth Route to InP Hollow Spheres and a Honeycomb‐Like Macroporous Framework

AbstractHollow spheres and a honeycomb‐like macroporous framework structure of InP have been successfully fabricated by employing Au/In core/shell composite colloid droplets formed in situ as the template and catalyst for a simple analogous solution‐liquid‐solid (ASLS) growth route. SEM images show that the morphology of the obtained InP is mostly micrometer‐scale hollow spheres (>80 %) accreted with honeycomb‐like structures (<5 %). These hollow spheres have well‐defined voids and homogeneous walls, and the surface of the obtained InP hollow spheres is porous, which indicates that the building blocks are InP nanoparticles formed by solidification on the surface of Au/In core/shell droplets. A possible growth mechanism for the micrometer hollow spheres and honeycomb‐like macroporous framework is proposed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Synthesis and electrochemical properties of InP nanocrystals

In this report, we present a new organometallic synthetic method to prepare nearly monodisperse InP nanoparticles using indium trifluoroacetate as the In precursor. Spherical particles of various sizes were prepared by modulating the growth duration. The optical and electrochemical properties were investigated and discussed with reference to band edge positions. This is the first report on the band edge position of quantum confined InP nanoparticles, which is a key parameter for development of electro-optic devices like solar cells and light-emitting diodes based on it.

Isovalent Doping Strategy for Manganese Introduction into III—V Diluted Magnetic Semiconductor Nanoparticles: InP:Mn.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Isovalent Doping Strategy for Manganese Introduction into III-V Diluted Magnetic Semiconductor Nanoparticles: InP:Mn

III−V based diluted magnetic semiconductor (DMS) nanoparticles of In(1-x)MnxP (x ≤ 0.0135) have been prepared by slow heating of the reagents in trioctylphosphine oxide (TOPO) or by high-temperature injection of reagents dissolved in trioctylphosphine (TOP) into hot TOPO. The materials were prepared using either Mn(II) or Mn(III) salts as dopants and the resulting nanoparticles have diameters ranging from 2.95 ± 0.39 to 4.77 ± 0.73 nm, as determined from transmission electron micrographs. Chemical analysis of surface-exchanged samples revealed the incorporation of Mn into the crystal lattice with up to 6 Mn atoms per 3.4-nm diameter particle, or the equivalence of ∼1020 Mn atoms/cm3 in a zinc blende bulk lattice. The InP:Mn nanoparticles exhibited a red shift in the room-temperature photoluminescence of 0.02−0.03 eV relative to that for pure InP nanoparticles. Electron paramagnetic resonance studies suggest that the Mn atoms mostly reside near the surface and are Mn2+, regardless of the oxidation state of...

Infrared and Raman spectroscopies of InP/II–VI core-shell nanoparticles

We use infrared (IR) and Raman spectroscopies to investigate the optically active phonon modes in InP nanoparticles and InP/II–VI core-shell nanoparticles fabricated by similar colloidal chemistry methods. The IR transmission spectra of several InP nanoparticle samples exhibit a common absorption feature, which we assign to the Fröhlich mode. The Raman results for the same samples show transverse and longitudinal optical phonon peaks, and scattering strength in between due to surface optical (SO) modes. Infrared spectra of the InP/ZnSe core-shell nanoparticles ( T = 8 – 300 K ) exhibit three absorption features, one due to the InP core, and the others associated with the ZnSe shell layer. Raman measurements (12–292 K) also show three phonon-related peaks, whose intensities vary sharply with temperature. The frequencies of the IR and Raman lines are in approximate accord with dielectric continuum theory.

Investigation of ZnS Passivated InP Nanocrystals by XPS

ZnS passivated InP nanoparticles prepared by the TOP/TOPO method have been investigated by photoelectron spectroscopy with tunable synchrotron radiation. Based on the energy dependence of the electron escape depth, we present a method to characterize the core−shell nature of the sample structure. Energy tuning indicates that In is confined to the core of the particles while Zn is located in a surrounding shell. Computer simulation allows us to quantify these results and to extract average layer thicknesses.

Preparation and optical properties of composite thin films with embedded InP nanoparticles

InP nanoparticles embedded in SiO2 thin films were prepared by radio-frequency magnetron co-sputtering. We analyzed the structure and growth behavior of the composite films under different preparation conditions. X-ray diffraction and Raman spectroscopy analyses indicate that InP nanoparticles have a polycrystalline structure. The average size of InP nanoparticles is in the range of 3–10 nm. The broadening and red shift of the Raman peaks were observed, which can be interpreted by the phonon confinement model. Optical transmission spectra indicate that the optical absorption edges of the films can be modulated in the visible light range. The marked blue shift of the absorption edge with respect to that of bulk InP is explained by the quantum confinement effect. The theoretical values of the blue shift predicted by the effective mass approximation model are different from the experimental results for the InP-SiO2 system. Analyses indicate that the exciton effective mass of the InP nanoparticles is not constant and is inverse relative to the particles radius, which may be the main reason that results in the discrepancy between the theoretical and the experimental result. We discussed the possible transition of the direct band gap to the indirect band gap for InP nanoparticles embedded in SiO2 thin films.

Continuous and Time Resolved Optically Detected Magnetic Resonance Studies of InP Nanoparticles

AbstractCarriers in small colloidal InP nanoparticles are in strong quantum confinement regime. The low temperature photoluminescence spectrum of InP nanoparticles is composed of an excitonic luminescence at high energies and a non-excitonic defect emission band at lower energies. HF etching of the nanoparticles reduces the defect emission and enhances the exciton process.In this work we apply optically detected magnetic resonance spectroscopy (ODMR) both in continuous wave and time resolved mode (TR-ODMR) to study the defect luminescence in InP nanoparticles. The results show that the defect luminescence originates from weakly coupled electron-hole pair, where the electron is trapped at the surface by phosphorous vacancy, Vp, and the hole is located at the valence band. Additionally, the results suggest that the non-etched samples are dominated by Vp at the surface. Those are mainly eliminated upon HF treatment, leaving behind small percent of Vp in the core of the nanoparticle. We also find the electron-hole exchange interaction from circular polarized ODMR measurements. The TR-ODMR measurement further clarifies the spin dynamics and characteristic of the magnetic sites. Fitting these measurements to the simulated response of the PL intensity to the square wave modulated microwave power revealed that the spin relaxation time and radiative lifetime of electron-hole pair in the nanoparticles are in the microseconds regime.

Excited-state spectroscopy of InP quantum dots

We have measured low-temperature size-selective photoluminescence excitation spectra of high-quality InP quantum dots prepared by collodial chemistry. A set of samples with mean emission energies in the range from 1.9 to 2.2 eV was investigated. All samples have a size distribution of about 10%, resulting in an inhomogeneously broadened photoluminescence lineshape. Due to the finite size distribution, spectra were collected at different detection wavelengths to reveal the energies of the excited excitonic states. The size dependence of the quantization energies of InP nanoparticles was determined by measuring photoluminescence excitation at different detection energies within one sample. Up to eight excited-state transitions in a set of seven samples were observed, as the estimated quantum dot size was scanned from 1.8 to 4.0 nm. A comparison of the observed peaks with a six-band $\mathbf{k}\ensuremath{\cdot}\mathbf{p}$ calculation is given. In contrast to the successful interpretation in the case of CdSe, no agreement between the calculated and the observed excited-state energies is achieved.