Quantum Size Confinement Effect Research Articles

Magnetic field and anisotropic parabolic potential effects on ground state binding energy of impurity magnetopolaron in asymmetrical semi-exponential quantum wells

We performed the ground state binding energy (GSBE) and vibrational frequency (VF) of strong-coupling impurity magnetopolaron (SCIM) in asymmetrical semi-exponential quantum wells (ASEQWs) containing a hydrogen-like impurity in the center exposed to a uniform magnetic field through Lee-Low-Pines unitary transformation and linear combination operation method based on effective mass approximation. The results were expressed as functions of GSBE and VF for different magnetic field cyclotron frequency (MFCF) and Coulombic impurity potential (CIP) strength, the positive criteria of ASEQWs along the growth direction of QW and effectual confinement lengths of APCP along the coordinates were analyzed. Our findings revealed that the VF and GSBE were enhanced by increasing magnetic field cyclotron frequency and the parameter of asymmetrical semi-exponential confinement potential (ASECP), which was increased by reducing APCP effectual confinement length along the directions of coordinates. The above observations could be because of quantum size confinement effects.

Physical Origin of Dual-Emission of Au-Ag Bimetallic Nanoclusters.

On the origin of photoluminescence of noble metal NCs, there are always hot debates: metal-centered quantum-size confinement effect VS ligand-centered surface state mechanism. Herein, we provided solid evidence that structural water molecules (SWs) confined in the nanocavity formed by surface-protective-ligand packing on the metal NCs are the real luminescent emitters of Au-Ag bimetal NCs. The Ag cation mediated Au-Ag bimetal NCs exhibit the unique pH-dependent dual-emission characteristic with larger Stokes shift up to 200 nm, which could be used as potential ratiometric nanosensors for pH detection. Our results provide a completely new insight on the understanding of the origin of photoluminescence of metal NCs, which elucidates the abnormal PL emission phenomena, including solvent effect, pH-dependent behavior, surface ligand effect, multiple emitter centers, and large-Stoke’s shift.

Ultrasmall CsPbBr3 Quantum Dots with Bright and Wide Blue Emissions

Low‐dimensional metal halide perovskites have been widely regarded due to their unique crystal structure and photophysical properties. Herein, blue‐emission CsPbBr3 quantum dots (QDs) or nanocrystals (NCs) with extremely small crystal size (1–2 nm) but high photoluminescence quantum yield (PLQY, 72.4%) are synthesized with a new surface ligand, single (6‐amino‐6‐deoxy) beta cyclodextrin (6A‐βCD), which also acts as the confined‐growth template for such small QDs. Detailed photoluminescence spectrum and femtosecond transient absorption spectrum study proves that the blue emission with multiple peaks originates from both band‐edge radiation and exciton recombination. Furthermore, as a result of the small size, exciton localization in the form of self‐trapped excitons (STEs) and significant quantum size confinement effect are both important reasons for the efficient and wide blue emissions of these QDs. This work provides a new strategy not only to synthesize ultrasmall perovskite QDs but also to develop blue perovskite‐QD light‐emitting devices.

Band Gap Narrowing in Silane-Grafted ZnO Nanocrystals. A Comprehensive Study by Wide-Angle X-ray Total Scattering Methods

Zinc oxide (ZnO) is a largely investigated semiconducting nanomaterial for photocatalytic applications and is an excellent active layer candidate in photovoltaics. Among native defects, having a primary role in ZnO optoelectronic properties, the influence of nearly ubiquitous planar faults of wurtzite sequences in ultrasmall (≤5 nm) nanocrystals (NCs) remains poorly understood. Here, we present a thorough study of ZnO NCs prepared under morphological control of covalently grafted vinyltrimethoxysilane (VTMS) and exhibiting either narrowing or widening of the band gap upon NCs downsizing, depending on the NC growth rate. By using synchrotron X-ray total scattering data, atomistic models and the Debye Scattering Equation (DSE) method, complemented by spectroscopic (FTIR and UV–vis) investigations, we provide a comprehensive quantitative picture in which effects from planar defects are disentangled from those due to NC size, morphology, and lattice strain (here controlled by preferential binding of VTMS on the ZnO basal faces). When faults occur in high concentration (linear density up to 1.6 × 10⁶ cm–¹), NCs exhibit optical band gap narrowing (3.27 eV vs 3.37 eV in bulk ZnO), whereas gap widening (3.52 eV) is observed at a lower density (0.8 × 10⁶ cm–¹), at which quantum-size confinement effects prevail. Supported by photoluminescence and photodegradation experiments, surface defect passivation by VTMS, affecting visible emissions and photocatalytic properties of ZnO, is also discussed in relation to silane coating and fault-driven bandgap. This work sheds light on the complex interplay among planar defects, quantum size effect, and surface modifications in ultrasmall ZnO NCs and on the importance of advanced X-ray total scattering methods toward atomically precise control of defects in nanostructures.

Exploring Rapid Photocatalytic Degradation of Organic Pollutants with Porous CuO Nanosheets: Synthesis, Dye Removal, and Kinetic Studies at Room Temperature

In this work, we report the facile, environmentally friendly, room-temperature (RT) synthesis of porous CuO nanosheets and their application as a photocatalyst to degrade an organic pollutant/food dye using NaBH4 as the reducing agent in an aqueous medium. Ultrahigh-resolution field effect scanning electron microscopy images of CuO displayed a broken nanosheet-like (a length of ∼160 nm, a width of ∼65 nm) morphology, and the lattice strain was estimated to be ∼1.24 × 10–3 using the Williamson–Hall analysis of X-ray diffraction plots. Owing to the strong quantum size confinement effect, CuO nanosheets resulted in an optical energy band gap of ∼1.92 eV, measured using Tauc plots of the ultraviolet–visible (UV–vis) spectrum, resulting in excellent photocatalytic efficiency. The RT synthesized CuO catalyst showed a high Brunauer–Emmet–Teller surface area of 30.88 ± 0.2313 m2/g (a correlation coefficient of 0.99972) with an average Barrett–Joyner–Halenda pore size of ∼20.385 nm. The obtained porous CuO nanosheets exhibited a high crystallinity of 73.5% with a crystallite size of ∼12 nm and was applied as an efficient photocatalyst for degradation of the organic pollutant/food dye, Allura Red AC (AR) dye, as monitored by UV–vis spectrophotometric analysis and evidenced by a color change from red to colorless. From UV–vis spectra, CuO nanosheets exhibited an efficient and ultrafast photocatalytic degradation efficiency of ∼96.99% for the AR dye in an aqueous medium within 6 min at RT. According to the Langmuir–Hinshelwood model, photodegradation reaction kinetics followed a pseudo-first-order reaction with a rate constant of k = 0.524 min–1 and a half-life (t1/2) of 2.5 min for AR dye degradation in the aqueous medium. The CuO nanosheets showed an outstanding recycling ability for AR degradation and would be highly favorable and an efficient catalyst due to the synergistic effect of high adsorption capability and photodegradation of the food dye.

Sol-gel derived Al-doped ZnO nanoplates: Structural and optical properties

In the present work, undoped and Al-doped ZnO nanoplates have been prepared by sol–gel method and investigated their structural, morphological and optical properties. Structural analysis has been performed by powder X-ray diffraction (XRD) pattern. The XRD results exhibited that the synthesized nanostructures have hexagonal wurtzite phase of ZnO. Scanning electron microscopy (SEM) depicts the formation of nanoplates. The optical properties of the prepared samples have been studied using UV–visible (UV–vis) absorption and photoluminescence (PL) spectroscopy at 300 K. UV–vis absorption spectra revealed a large blue shift in absorption peak indicates quantum size confinement effect. Red-shifted absorbance peak is obtained for higher doping concentration of Al that may be attributed to change of the surfaces for nanoplates. PL spectra of undoped and Al-doped ZnO NPs have band edge luminescence in UV region and defects related optical emission such as violet emission at ~417 nm, blue emission at ~441 nm, blue–green emission at ~484 nm and green emission at ~524 nm in visible region. A significant enhancement of the PL intensity has been observed in 3 wt% Al-doped ZnO sample as compared to undoped ZnO which may be assigned to transformation of nanoclusters to nanoplates.

Relationship between the Photoluminescence Spectra and IR Spectroscopy of Mesoporous Silicon Samples during Long-Term Storage: The Effect of Immersion in an Aqueous Fe(NO<sub>3</sub>)<sub>3</sub> Solutions

The article provides a comparative analysis of changes in the PL spectra and infrared spectroscopy (IR) with reference and immersion samples of mesoporous silicon during long-term storage in air at room temperature. Immersion was carried out in an aqueous solution of iron nitrate (Fe (NO3)3) with a concentration of 0.2 M and 0.5 M with three times: 5, 10 and 20 minutes. An analysis of the FIR data for etalon and immersion samples showed a number of features found during long-term storage of mesoporous silicon: (1) a sharp decrease in the density of hydride bonds; (2) the polynomial nature of the growth of O3-SiH and Si-OH bonds saturating dangling bonds; and (3) the polynomial growth of silicon dioxide with the formation of oxygen defects. It was found that after immersion in a solution of 0.5 M Fe (NO3)3 for 10 minutes, a more intense increase in the PL in mesoporous silicon is observed while maintaining its nanostructure after 200 days of storage compared with the etalon sample, for which a weak quantum size confinement (QSC) is observed. The main mechanism of photoluminescence increase in mesoporous silicon during long-term storage is radiative recombination from oxygen defect levels, not from a QSC effect.

Relationship between the Photoluminescence Spectra and IR Spectroscopy of Mesoporous Silicon Samples during Long-Term Storage: The Effect of Immersion in an Aqueous LiBr Solutions

Studies are devoted to determining the effect of long-term storage (up to 200 days) of untreated and immersion-treated layers of mesoporous silicon in an aqueous lithium bromide solution obtained by anodizing with a current density of 10 mA/cm2 in electrolyte HF: CH3OH = 2: 1. It was found that an increase in the PL intensity and its saturation with a storage time of more than 100 days in all samples is observed. A detailed analysis of absorbance on bonds in m/por-Si showed that during storage, hydrogen bonds are destroyed, and the PL peak intensity is proportional to the increasing concentration of non-stoichiometric oxide, in which oxygen atoms forms radiative states. It was shown that in the treated samples, the PL intensity decreases with increasing immersion time, but the mechanism of photoluminescence through the quantum size confinement (QSC) effect in mesoporous silicon without and with immersion in an aqueous LiBr solution is not significant.

Ligand induced anomalous emission shift of size-controlled CsPbBr3 nanocrystals

CsPbX3 perovskite nanocrystals (NCs) have attracted much attention from researchers because of their excellent photoelectric properties like high quantum yield, large absorption cross section, and simple preparation process. The addition of ligands in the synthesis process has a significant effect on the microstructure and photophysical properties of solution-processed NCs, which needs further extensive studies. In this Letter, the effects of ligand electronegativity on the size and photoluminescence (PL) properties of CsPbBr3 NCs were reported. One is typical oleic acid with weak electronegativity, and another is 2-acrylamide-2-methylpropionic sulfonic acid with strong electronegativity. The third is their typical mixture with a molar ratio of 1:1. With the increase in ligand electronegativity, the size of CsPbBr3 NCs increases significantly. However, in contrast to the traditional quantum size confinement effect, the PL peak exhibits an abnormal blue shift gradually and the ligand passivation effect on NC surface defects also becomes more significant. The physical mechanism of this anomalous PL shift phenomena of CsPbBr3 NCs was investigated using the time-resolved PL spectrum and transient absorption spectrum.

Controlled Synthesis, Formation Mechanism, and Applications of Colloidal Ag8SnS6 Nanoparticles and Ag8SnS6/Ag2S Heterostructured Nanocrystals

Semiconductor nanocrystals (SC NCs) have attracted scientists’ attention because of their size- and shape-dependent optical properties. Now, many scientists’ research is focused on the synthesis of the earth-abundant and environmentally compatible SC NCs and their applications for solar energy conversion. Herein, colloidal silver-based I–IV–VI SC NCs, Ag8SnS6 nanoparticles (NPs) were synthesized. Ag8SnS6 NPs showed a strong quantum size confinement effect from optical measurement. The photocurrent response measurement showed a typical n-type property for Ag8SnS6 NPs. It is very interesting that colloidal Ag8SnS6/Ag2S heterostructured nanocrystals (HSNCs), containing drop-shaped and little bowtie-shaped HSNCs, can also be synthesized via changing the adding process of precursors in the beginning of the experiment. The first formation of Ag NPs is very important to form Ag8SnS6/Ag2S HSNCs. A seeded growth mechanism was proposed to explain the formation of Ag8SnS6/Ag2S HSNCs. The polycrystalline structure in...

Bioengineered II–VI semiconductor quantum dot–carboxymethylcellulose nanoconjugates as multifunctional fluorescent nanoprobes for bioimaging live cells

Colloidal semiconductor quantum dots (QDs) are light-emitting ultra-small nanoparticles, which have emerged as a new class of nanoprobes with unique optical properties for bioimaging and biomedical diagnostic. However, to be used for most biomedical applications the biocompatibility and water-solubility are mandatory that can achieved through surface modification forming QD-nanoconjugates. In this study, semiconductor II–VI quantum dots of type MX (M=Cd, Pb, Zn, X=S) were directly synthesized in aqueous media and at room temperature using carboxymethylcellulose sodium salt (CMC) behaving simultaneously as stabilizing and surface biofunctional ligand. These nanoconjugates were extensively characterized using UV–visible spectroscopy, photoluminescence spectroscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, dynamic light scattering and zeta potential. The results demonstrated that the biopolymer was effective on nucleating and stabilizing the colloidal nanocrystals of CdS, ZnS, and PbS with the average diameter ranging from 2.0 to 5.0nm depending on the composition of the semiconductor core, which showed quantum-size confinement effect. These QD/polysaccharide conjugates showed luminescent activity from UV–visible to near-infrared range of the spectra under violet laser excitation. Moreover, the bioassays performed proved that these novel nanoconjugates were biocompatible and behaved as composition-dependent fluorescent nanoprobes for in vitro live cell bioimaging with very promising perspectives to be used in numerous biomedical applications and nanomedicine.

Synthesis and investigations of In2S3:Ho3+quantum dots on doping induced changes

Diluted magnetic semiconductor (DMS) quantum dots have been investigated extensively because of their potential applications in spintronic devices that combine the charge and spin properties of electrons in a material. Herein, the In2S3:Ho3+ quantum dots (3–5 nm) with different doping concentrations have been synthesized using the facility built by us and the corresponding growth mechanism is proposed and discussed in detail. We investigated the effect of different Ho3+ content on the optical and magnetic properties. The absorption and emission spectra exhibit a strong quantum size confinement effect and a large Stokes shift. The band gap energy can be tuned by doping concentration varying from 3.19 to 3.62 eV. The emission processes are assigned to the excitonic recombination and near-doping/near-defect excitonic luminescence, respectively. Excess Ho3+ content reduces the intensity of photoluminescence as a result of concentration quenching. Room temperature ferromagnetism is observed from VSM measurement. The change of saturation magnetizations with various Ho3+ doping concentrations is explained and discussed based on BMP theory. In addition, the band gap distribution and the chemical bonding mechanism are clearly illustrated using VASP first-principles calculations. This study provides experimental and theoretical guidance for designing and synthesizing unique spintronic materials, which can promote the development of spintronic applications.

Nanotexturing To Enhance Photoluminescent Response of Atomically Thin Indium Selenide with Highly Tunable Band Gap.

Manipulating properties of matter at the nanoscale is the essence of nanotechnology, which has enabled the realization of quantum dots, nanotubes, metamaterials, and two-dimensional materials with tailored electronic and optical properties. Two-dimensional semiconductors have revealed promising perspectives in nanotechnology. However, the tunability of their physical properties is challenging for semiconductors studied until now. Here we show the ability of morphological manipulation strategies, such as nanotexturing or, at the limit, important surface roughness, to enhance light absorption and the luminescent response of atomically thin indium selenide nanosheets. Besides, quantum-size confinement effects make this two-dimensional semiconductor to exhibit one of the largest band gap tunability ranges observed in a two-dimensional semiconductor: from infrared, in bulk material, to visible wavelengths, at the single layer. These results are relevant for the design of new optoelectronic devices, including heterostructures of two-dimensional materials with optimized band gap functionalities and in-plane heterojunctions with minimal junction defect density.

STRUCTURAL AND OPTICAL PROPERTIES OF CD1-XZNXS ALLOY QUANTUM DOTS

Cd1-xZnxS (0≤x≤1) alloy quantum dots (QDs) were synthesized via coprecipitation method using cetyltrimethyl ammonium bromide (CTAB) as a capping material. Elemental composition of the investigated samples was determined by the energy dispersive x-ray spectroscopy (EDX). X-ray powder diffraction (XRD) and high resolution transmission electron microscope (HRTEM) were used to characterize the crystalline structure, particle size and morphology. XRD analysis indicated that the as synthesized nanomaterials, except for ZnS, have a mixture of cubical and hexagonal phases. The percentage of the hexagonal phase was very small. ZnS nanocrystal has a cubical structure. The particle size and the lattice constant decreased with the increase of Zn content. HRTEM data showed the presence of QDs and confirmed the XRD results. Ultraviolet-visible (UV-vis) absorption spectroscopy was employed to study the optical properties. Absorption band edges showed blue-shift systematically with the increase of Zn content. The results are interpreted in terms of the quantum-size confinement effect. Measurements of XRD and UV-vis absorption spectra under different annealing temperatures up to 400°C were performed. The annealed compositions showed mixture of cubical and hexagonal crystal structure. Tendency for phase transformation, from cubic to hexagonal upon annealing were observed. The degree of tendency for phase transformation increased with the decrease of Zn content and the increase of the annealing temperature. Particle sizes were increased with increasing the annealing temperature. UV- vis absorption spectra exhibited red-shift systematically with the increase of the annealing temperature. The values of the optical band gap energies decreased with increasing annealing temperature.

Cadmium sulfide quantum dots stabilized by castor oil and ricinoleic acid

Castor oil and ricinoleic acid (an isolate of castor oil) are environmentally friendly bio-based organic surfactants that have been used as capping agents to prepare nearly spherical cadmium sulfide quantum dots (QDs) at 230, 250 and 280°C. The prepared quantum dots were characterized by Ultra violet–visible (UV–vis), Photoluminescence (PL), Transmission Electron Microscopy (TEM), High Resolution Transmission Electron Microscopy (HRTEM) and X-ray diffraction (XRD) giving an overall CdS QDs average size of 5.14±0.39nm. The broad XRD pattern and crystal lattice fringes in the HRTEM images showed a hexagonal phase composition of the CdS QDs. The calculated/estimated average size of the prepared castor oil capped CdS QDs for various techniques were 4.64nm (TEM), 4.65nm (EMA), 5.35nm (UV–vis) and 6.46nm (XRD). For ricinoleic acid capped CdS QDs, the average sizes were 5.56nm (TEM), 4.78nm (EMA), 5.52nm (UV–vis) and 8.21nm (XRD). Optical properties of CdS QDs showed a change of band gap energy from its bulk band gap of 2.42–2.82eV due to quantum size confinement effect for temperature range of 230–280°C. Similarly, a blue shift was observed in the photoluminescence spectra. Scanning electron microscope (SEM) observations show that the as-synthesized CdS QDs structures are spherical in shape. Fourier transform infra-red (FTIR) studies confirms the formation of castor oil and ricinoleic acid capped CdS QDs.

(Invited) Effect of Individual Dopants in Nano-SOI-MOSFETs and Nano-pn-Diodes

Introduction In recent years, novel MOSFET characteristics dominated by a single dopant-atom were reported by several groups [1-4], where carrier transport mechanism is tunneling through individual dopant atoms. In this background, we have proposed and demonstrated a variety of dopant-atom devices, i.e., dopant-atom (DA) transistors [4], DA memories [5], DA turnstiles [6-8] and DA photonic devices [9-11]. In those devices, only one or a few dopants are intentionally used and one dopant works as a quantum well for electron (or hole) tunneling transport. Here, we present a brief overview of such devices from experimental and theoretical point of view. P-donor in nano-Si When we focus on a phosphorous (P) donor atom, it is known that the ionization energy, or the binding energy, with respect to the Si conduction band minimum, is ~45 meV. Therefore, single-electron tunneling P-atom devices can operate only at low temperatures, below ~20 K, since at high temperatures electrons are thermally excited and tunneling transport mechanism does not work. However, when a dopant is embedded in sufficiently small Si structures, its ionization energy is enhanced due to dielectric and quantum size confinement effects [12], leading to high-temperature operation. Recently, we have demonstrated operation of donor-atom SOI-MOSFETs at around 100 K in specifically-designed nano-stub-channels [13]. A good correlation is found between the operation temperature and binding energy (E a), with the highest SET-operation temperature being achieved for a P donor with E a≅ 100 meV [13]. A few coupling donors So far, in most investigated dopant-atom devices, the dopants were introduced in random positions. Only a few works addressed directly the control of dopants, either in number, using single ion implantation [14], or in position, with atomic manipulation using scanning tunnelling microscope tips [15]. Most recently, we have challenged a more practical and simpler doping technique using nanoscale doping masks [16]. The channel of SOI-MOSFET was selectively doped within an area of ~30 nm in width by the conventional diffusion process. Even in such a classical doping process, the number of dopants in the doped area may be controlled to around 5. I-V characteristics measured for these selectively-doped FETs are consistent with the model [16]. Nano-pn junctions Individuality of dopants appears not only in nano-FETs, but also in nano-pn diodes. In fact, we have reported dopant-induced random telegraph signals (RTS) in nanoscale pn diodes [17], and attributed the RTS to charging and discharging of a single dopant near the pn junction. Observation of dopant potential In research of dopant-atom devices, it is extremely important to establish an observation tool to monitor dopants’ positions and their individual potentials. For this purpose, we have developed low-temperature Kelvin probe force microscopy (LT-KFM) which allows measurements of devices under regular operation. Using this technique, we succeeded in detection of potential profiles due to individual dopants and potential changes due to single-electron injection effects [18-21].

Synthesis and photoluminescence property of silicon carbide nanowires thin film by HF-PECVD system

A sample and scalable synthetic strategy was developed for the fabrication of nanocrystalline SiC (nc-SiC) thin film. Thin sheet of nanocrystalline diamond was deposited on Si substrate by hot filament-assisted plasma-enhanced chemical vapour deposition system (HF-PECVD). Further, the resulting carbon-based sheet was heated at 1200 °C to allow a solid state reaction between C and Si substrate to form the SiC thin films. The synthesized films mainly consist of β-SiC nanowires with diameters of about 50 nm and tens of micrometers long. The nanowires axes lie along the [1 1 1] direction and possess a high density of planar defects. The β-SiC nanowires thin films exhibit the strong photoluminescence (PL) peak at a wavelength of 400 nm, which is significantly shifted to the blue compared with the reported PL results of SiC materials. The blue shift may be ascribed to morphology, quantum size confinement effects of the nanomaterials and abundant structure defects that existed in the nanowires.

Synthesis and characterization of ZrO2–CuO co-doped ceria nanoparticles via chemical precipitation method

In the present study, the fluorite cubic phase of bare and ZrO2–CuO co-doped ceria (CeO2) nanoparticles have been synthesized through a simple chemical precipitation method. X-ray diffraction results revealed that average grain sizes of the samples are within 5–6nm range. The functional groups present in the samples were identified by Fourier Transform Infrared Spectroscopy (FTIR) study. Surface area measurement was carried out for the ceria nanoparticles to characterize the surface properties of the synthesized samples. The direct optical cutoff wavelength from DRS analysis was blue-shifted evidently with respect to the bulk material and indicated quantum-size confinement effect in the nanocrystallites. PL spectra revealed the strong and sharp UV emission at 401nm. The surface morphology and the element constitution of the pure and doped nanoparticles were studied by scanning electron microscope fitted with energy dispersive X-ray spectrometer arrangement. The thermal decomposition course was followed using thermo gravimetric and differential thermal analyses (TG-DTA).

Synthesis and Characterization of ZnO Nanoparticles Templated by SBS-OH

ZnO nanoparticles were synthesized by using N, N-dimethylformamide as solvent and poly(styrene-b-butadiene-b-styrene) SBS-OH as stablizer at 100°C through “in situ” reaction process. The optical properties and morphologies for the synthesized ZnO nanoparticles were measured through UV-Vis, PL and TEM methods. The results show that corona-embedded ZnO nanoparticles could be obtained by SBS-OH micelles in polar solvent DMF. The obtained ZnO nanoparticles could give an apparent quantum size confinement effects and PL results show that ZnO nanoparticles could give good luminescence properties.

SYNTHESIS AND MORPHOLOGY OF SILICON NANOPARTICLES BY DEPOSITION TIME VARYING LPCVD METHOD TO DEMONSTRATE THE VARIATION OF HEIGHT, DENSITY AND SIZE

The confinement of the modern day semiconductor dev ices is fast propelling the growth of nanoparticles as an excellent constituent of such device and the characteristics like quantum si ze confinement and coulomb blockade effect of the sis accelerating their application in this field. But before the fabrication of devices with the nanoparticles, their morphol ogical and electrical characteristics needs to be studied in order to hav e a sense about the efficiency of such a device. In this experiment, Silicon nanoparticles have been deposited on SiO 2 substrate by thermal decomposition of silane using Low Pressure Chemical Vapor Deposition (LPCVD) Method with varying deposition t imes. Then, the morphology of the sample, the size as well as distribution of the nanoparticles is investigated using Atomic Force Mi croscopy (AFM) and the Scanning Probe Image Process or (SPIP). It shows that all the characteristics of the nanoparticles like h eight, density and size of the nanoparticles change with the varying deposition time. The size of the nanoparticles varied between 2-10nm whereas the height and density varied between 1-3n m and 2X10 11 /cm 2 3.5X10 11 /cm 2 respectively.