Indium Nanoclusters Research Articles

Non-radiative energy transfer in quantum dot ensemble mediated by localized surface plasmon

Exciton-plasmon interaction was studied experimentally in structures with InAs/AlGaAs quantum dots (QDs) and indium nanoclusters grown by molecular beam epitaxy. In photoluminescence (PL) spectra, a strong enhancement of low energy QDs was observed that resulted in a new peak. This effect is explained with the plasmon-assisted energy transfer from an ensemble of donor QDs located under a metal cluster to a low energy acceptor QD. The dependence of the integrated PL signal of the low new peak on the QD number under an individual metal cluster changed from linear to quadratic and revealed the transition from a single to many interacting QDs.

Plasmonic reflectance anisotropy spectroscopy of metal nanoparticles on a semiconductor surface

A theory of plasmonic differential anisotropic reflection of light from nanoparticles located near the interface between media is developed. The model of a monolayer consisting of identical ellipsoidal metal particles occupying sites of a rectangular lattice is investigated. Effective plasmonic polarizabilities of nanoparticles in the layer are calculated self-consistently using the Green’s function technique in the quasipoint dipole approximation. The local-field effect caused by anisotropic dipole plasmons of particles in the layer and their image dipoles is taken into account. The lately observed resonant reflectance anisotropy spectra of indium nanoclusters on InAs surface are explained by the difference between frequencies of plasmons with the orthogonal polarizations in the surface plane. The difference between the plasmon frequencies is attributed to anisotropy of the particles shape or/and the layer structure; the signs of frequency difference for the two types of anisotropy being different.

Reflectance anisotropy spectroscopy of metal nanoclusters formed on semiconductor surface

Optical anisotropy of indium nanoclusters formed on the (001) surface of indium arsenide was found by differential reflectance anisotropy spectroscopy. The fact of such an observation for nanocluster arrays unambiguously evidences the presence of their macroscopic anisotropy which could not be disclosed by conventional diagnostics techniques. The scale of the observed plasmonic anisotropy signal exceeds by two orders of magnitude the scale of anisotropy signals from valence-bond structures formed on a semiconductor surface. A resonant feature observed in reflectance anisotropy spectra is interpreted in the model of coupled dipole plasmons belonging to ellipsoidal nanoparticles. Estimation based on the experimental spectra shows that within the sample surface the lengths of ellipsoid semiaxes differ from each other by a few percent.

Study of Ultraviolet Emission Enhancement in AlxInyGa1–x–yN Quaternary Alloy Film

The effect of indium cluster on enhanced ultraviolet luminescence in AlxInyGa1–x–yN quaternary alloys with increasing Al composition was investigated. X-ray diffraction (XRD), temperature-dependent photoluminescence (PL), transmittance spectra, and Raman scattering measurements have been employed to study the AlxInyGa1–x–yN quaternary alloy. Abnormal S-shaped temperature dependence of PL emissions in high Al content sample originated from carrier localization induced by indium nanoclusters, which is in good agreement with the pure InN mode measured by Raman scattering. A large Stokes shift between the emission peak and the absorption edge is also found in the high Al content sample. All these observations suggested that the enhancement of carrier localization by indium nanoclusters is responsible for the increase in radiative recombination probability with increasing Al composition. Our results demonstrated that AlxInyGa1–x–yN quaternary alloy can exhibit a larger band gap than that of GaN and enhanced ul...

Oxidation of ion beam synthesised embedded indium nanoclusters in silica

The paper discusses the results of a study on the formation of indium oxide nanoclusters in silica samples implanted with high energy indium ions. Trace quantities of indium oxide were found on as-implanted samples. On annealing in vacuum/oxygen atmosphere significant increase in the quantity of indium oxide phase was observed. A mechanism is proposed for the formation of indium oxide and is mainly attributed to the reaction of metallic indium with the oxygen released from the silica matrix by ballistic process. During annealing in oxygen atmosphere the oxygen diffusing into the silica also plays a role in the oxidation of indium NCs.

Indium on a copper phthalocyanine thin film: Not a reactive system

The chemical and electronic structure of indium-on-copper phthalocyanine (CuPc) contacts is addressed. Both core levels and valence-band evolutions were inspected during the incremental formation of the indium-CuPc interface. In contrast to the previous study [V. Y. Aristov et al., Phys. Rev. B 72, 165318 (2005)], our results suggest that the In-CuPc system is not a reactive one. This is corroborated by the absence of reactive components in the $\text{C}\text{ }1s$ and $\text{N}\text{ }1s$ regions. A component shifted toward high binding energy in the $\text{In}\text{ }4d$ spectrum and gap states---the latter emerging between the highest-occupied molecular orbital and the Fermi level, which were regarded as an evidence of a reaction between In and CuPc---are consistently interpreted in terms of the final-state effect of finite indium nanoclusters exposed at the CuPc surface.

Stability of Embedded Indium Nanoclusters in Silica Under Thermal Treatment and Ion Irradiation

The stability of embedded Indium (In) nanoclusters (NCs) in silica under thermal annealing and ion irradiation was investigated. The In NCs were prepared by implantation of 890 keV indium ions in silica matrix at room temperature. Post implantation annealing resulted in the shifting of the size distribution to higher side. On the other hand 140 keV Nitrogen ion irradiation at elevated temperature resulted in the reduction of NCs size, with significant narrowing of the size distribution. The paper discusses the results of the study in the light of the models pertaining to the stability of NCs under ion irradiation conditions.

Synthesis of indium nanoclusters and formation of thin film contacts on plastic substratesfor organic and flexible electronics applications

In this work, we described the processes of synthesizing free-standing indium nanoclustersusing inverse micelles and microemulsions as well as synthesizing organic-encapsulatedindium nanoclusters using alkanethiols as the organic encapsulants. The synthesizedorganic-encapsulated indium nanoclusters have demonstrated the feasibilities to beused as plastic compatible soft metal contacts for emerging organic devices. Thehomogeneously distributed indium nanoclusters with sizes of 10–30 nm have beenfabricated on a few different plastic substrates. By changing the alkanethiol carbonchain length and the sizes of the indium nanoclusters, the annealing temperaturerequired to form low-resistance indium thin film conductors has been reduced to80–100 °C, which is acceptable for a variety of organic thin films.

Formation and growth of embedded indium nanoclusters by In2+ implantation in silica

Indium nanoclusters are synthesized in an amorphous silica matrix using an ion-implantation technique. Indium ions (In2+) with energy of 890 keV are implanted on silica to fluences in the range of 3×1016–3×1017 cm-2. The formation of indium nanoclusters is confirmed by optical absorption spectrometry and glancing incidence X-ray diffraction studies. A low frequency Raman scattering technique is used to study the growth of embedded indium nanoclusters in the silica matrix as a function of fluence and post-implantation annealing duration. Rutherford backscattering spectrometry studies show the surface segregation of implanted indium. Photoluminescence studies indicate the formation of a small quantity of indium oxide phase in the ion-implanted samples.

Synthesis and stability of indium nanoclusters formed in silica by ion implantation

In this work, we report on the synthesis of indium crystalline nanoparticles by ion implantation of In2+ ions (2×1017In2+/cm2, 320keV) in silica. The thermal stability of the nanoparticles is investigated during a post-implantation thermal annealing cycle in vacuum by means of in situ techniques based on X-ray diffraction (XRD) and transmission electron microscopy (TEM). The measurements were carried out in a temperature range from room temperature up to 473K, which is above the bulk melting point of In (429.8K). The experimental results demonstrated that the In nanocrystals embedded in the silica matrix exhibit a range of melting temperatures between a lower limit of 423K corresponding to a melting point depression of 7K and an upper limit of 443K corresponding to a superheating of 13K. During the thermal cycle, all the particles remain stable in their positions and no clusters growth was observed. When the sample was cooled down a remarkable supercooling was observed, indicating the presence of a hysteresis cycle.

Spontaneous assembly of ordered nanoclusters and nanowires

AbstractA novel strategy for the spontaneous formation of spatially ordered nanoclusters and nanowires by taking advantage of templates is reported. With this method, a large‐scale perfectly ordered identical‐size indium nanocluster array and ordered indium nanowire array are obtained on Si(111)‐(7 × 7) and Si(001)‐2 × n, respectively. It can be applied also to other metals such as Ga, Al, Ag and Mn. The atomic structures of the indium nanoclusters and nanowires are determined by in situ scanning tunnelling microscopy analysis, combined with first‐principles theoretical calculations. The formation mechanism is discussed based on the results. Copyright © 2004 John Wiley & Sons, Ltd.

Spatially Ordered Quantum Dot Array of Indium Nanoclusters in Fully Indium-Exchanged Zeolite X

A spatially ordered quantum dot array of cationic indium nanoclusters has been synthesized in a single crystal of zeolite X. A single crystal of fully dehydrated and fully indium-exchanged zeolite X (ca. In87Si100Al92O384, In87−X) was exposed to 0.5 atm of H2S for 12 h at 673 K. After it was evacuated at temperature and cooled to 294 K, the crystal structure of the product (ca. In66Si100Al92O384, In66−X, a = 24.942(4) A) was determined by single crystal X-ray diffraction techniques in the cubic space group Fd3m. It was refined with all measured reflections to the final error index R1 = 0.058 for the 754 reflections with Fo > 4σ(Fo). X-ray photoelectron spectroscopy experiments confirmed the existence of both atomic and cationic indiums inside the single crystal. The 66 indium atoms or ions per unit cell were found at four crystallographically distinct positions, all on 3-fold axes. Eight In atoms at the sodalite unit centers and 32 Inca.2+ ions nearby (Inca.2+−In0 = 2.683(1) A), both filling their crysta...

Tuning of the plasmon absorption frequency of silver and indium nanoclusters via thin amorphous silicon films

Silver and indium nanoclusters have been incorporated into thin sputtered amorphous silicon films. The optical properties of these films have been investigated and compared with the results of spectra simulations. The dependence of the metal cluster plasmon resonance position on the silicon film thickness has been established. Additionally, the inhomogeneous broadening of the plasmon line has been estimated. The data are discussed with respect to the results of transmission electron microscopy.