Mechanism Of Light Emission Research Articles

White-Light Emission from Sputter Deposited TiOx Thin Film on Si Wafer

Solid state white light emitting devices (LEDs) are needed for the lighting and many other applications [1]. The semiconductor based LED can only emit the narrow band light due to the band gap energy restriction. The white light has to be generated by combining 3 different types of LEDs or using a LED and a phosphor material [2,3]. The single-chip white-light LED is desirable. Kuo and Lin reported a new type solid state LED that emits white light from an amorphous metal oxide film [4-7]. Light is emitted from conductive paths self-aligned to the gate electrode after the dielectric breakdown [4-7]. The TiOx thin film, which has a near zero band offset with Si, has been used as the gate dielectric in DRAMs [8,9]. It may be a good light emission material in the new type of LED. Authors investigated the TiOxbased LED for the electrical and optical properties. The new LED was made of the MOS capacitor on the p-type (100) Si wafer. The TiOx layer was sputter deposited from the Ti target at 5 mTorr, 60 W, and Ar/O2 (1:1) atmosphere for 2 minutes. The post deposition annealing (PDA) was done in the N2 atmosphere at 1,000°C for 3 min. The 80 nm ITO layer was sputter deposited on the sample and wet etched into the 300 µm diameter electrodes. The final post metal annealing (PMA) was done at 400°C for 5 min under the H2/N2(1:9) atmosphere. The current-voltage curves were measured with the Agilent 4155C semiconductor parameter analyzer. The light emission spectra were recorded by the optical emission spectrometer (StellarNet BLK-C-SR-TEC). Figure 1 shows the high-magnification photos of the LED stressed at Vg = -10V, -15V, -20V, and -25V, separately. The light is emitted from many discrete bright dots each of which is from the thermal excitation of a conductive path in the TiOx layer. The uniform light emission from the conventional semiconductor based LED is due to the recombination of the e-h pair or excitons. Both the light intensity and the number of bright dots in this LED increased with the increase of the magnitude of Vg (|Vg |). Figure 2 shows the current density-voltage (J-V) curve of a LED. The inset shows the enlarged view. The J jumped abruptly at the breakdown voltage (VBD ) of -5.9V above which the light emission was observed. Then, the leakage current increased monotonically with the increase of the |Vg | similar to the resistor behavior. The light emission mechanism of this device is the same as that of the incandescent light bulb, i.e., thermal excitation of the conductive filament from the passing of a large current. Figure 3 shows the emission spectra of the same LED at Vg = -10V, -15V, -20V, and -25V, separately. The same broad band light is emitted at different Vg ’s. The light intensity increases with the increase of the |Vg |, which is consistent with the Figs. 1 and 2 results. The device has a CIE 1931 color coordinate of (0.462, 0.426), which is located at the warm white light region. It has a CCT of 2,788K and a CRI Raof 95, which are close to those of the W incandescent light and better than those of many fluorescent or semiconductor-based LED lights. The new LED could be driven at various frequencies and duty cycles (DCs). The power consumption can be lowered with the reduction of the DC. Figure 4 shows the emission spectra of the LED driven from 1 Hz to 100 kHz but with the same DC of 75%. The light emission intensity, CIE color coordinates, CCT, and CRI remain the same, which is contributed by the fast excitation of the short conductive path, e.g., < 5 nm. This is desirable for many industry and biomedical applications. [1] J. M. Phillips et.al., Laser and Photon. Rev. 1, 307 (2007).[2] J. Kundu, et al., Nano Lett.12, 3031 (2012).[3] E. F. Schubert and J. K. Kim, Science 308, 1274 (2005).[4] Y. Kuo et al. , Appl. Phys. Lett. 102, 031117 (2013).[5] Y. Kuo et al., Electrochem. Solid-State Lett. 2, Q59 (2013).[6] Y. Kuo et al., Solid-State Electron. 89, 120 (2013).[7] C. C. Lin et al., J. Vac. Sci. Technol. B 31, 030605 (2013).[8] D. Wei, J. Solid State Sci. and Technol. 2,N110 (2013).[9] Q. Xie et al. Appl. Phys. Lett. 97, 112905 (2010).

Cytological changes during luminescence production in lanternshark (Etmopterus spinax Linnaeus, 1758) photophores

Studying an organism’s photogenic structures at the ultrastructural level is a key step in the understanding of its light-emission process. Recently, the photophore ultrastructure of the deep-sea lanternshark Etmopterus spinax Linnaeus, 1758 was described. The photocytes appeared to be divided into three areas including an apical granular area, which contains inclusions and was hypothesized to be the light-producing reaction site. In this study, we investigated the morphological changes occurring within the granular area during the bioluminescent emissions induced by two hormones: prolactin and melatonin. Prolactin provoked the formation of new structures in the granular area, the “grey particles”, whose number was proportional to the amount of light produced by the reaction. An increase in the number of granular inclusions was also detected at the end of the prolactin-induced light emission. Conversely, melatonin induced a decrease in the number of granular inclusions and an increase in their diameter. An effect of hormones was also observed on the iris-like structure where they triggered pigment retraction and hence an increase in the iris aperture diameter. This is consistent with previous findings and is shown for the first time at the cellular level. The possible role of grey particles in E. spinax light-emission mechanism is discussed, while granular inclusion is considered to be E. spinax’s intracellular luminescence site. Regarding typical shark long-lasting glows, a new term (“glowon”) is proposed to characterize this novel membrane-free microsource.

In silico study to breaking mystery of bioluminescence protein structure of bacterial luciferase and firefly luciferase

Bioluminescent proteins such as luciferase or green fluorescent protein become an interesting protein to be studied particularly on its structure, mechanism of light emission in certain wavelength and also its contribution in several applications. This study was conducted to understand more on the luciferase enzymes from bacteria and firefly based on in silico studies of their protein sequences, protein surface and interactions with different substrates. Protein crystal structures of bacterial luciferase and firefly luciferase that been deposited on Protein Data Bank (PDB) were used as model proteins for this study. Computer analysis of luciferase proteins such as pI prediction, multiple sequence alignment and molecular docking with different luciferase substrates (Flavin mononucleotide, L-luciferin, D-luciferin, vargulin, coelectrazine, Dinoflagellate luciferin, Latia luciferin) by using iGEMDOCK docking software had been conducted. Final analysis showed that, the bacterial luciferase prefers flavin mononucleotide and latia luciferin as its substrates and for firefly luciferase, it prefers dinoflagellate luciferin, L-luciferin and D-luciferin as the substrates. Bacterial luciferase and firefly luciferase shared very low protein sequence homology (&lt;30%) although they have similar catalyzing function. Prediction of pI by using ProtParam tool showed that bacterial luciferase and firefly luciferase has pI values of 4.95 and 6.42, respectively. In conclusion, bacterial and firefly luciferase can consider several different of luciferin in enzyme catalysis.

Basics of the decelerating black hole universe

Throughout the cosmic evolution, currently believed cosmic ‘critical density’ can be shown to be a default result of the ‘positively curved’ light speed rotating black hole universe ‘volume density’. As there is no observational or experimental evidence to Friedmann’s second assumption, the density classification scheme of Friedmann cosmology must be reviewed at fundamental level and possibly can be relinquished. The observed cosmic redshift can be reinterpreted as an index of ‘cosmological’ thermodynamic light emission mechanism. Clearly speaking during cosmic evolution, at any time in the past, in hydrogen atomemitted photon energy was always inversely proportional to the cosmic temperature. Thus past light emitted from older galaxy’s excited hydrogen atom will show redshift with reference to the current laboratory data. Note that there will be no change in the energy of the emitted photon during its journey from the distant galaxy to the observer. In no way ‘redshift’ seems to be connected with ‘galaxy receding’. By considering the ‘Stoney mass’ as the initial mass of the baby cosmic black hole, past and current physical and thermal parameters (like angular velocity, growth rate, age, redshift, thermal energy density and matter density) of the cosmic black hole can be understood. For a cosmic temperature of 3000 K, obtained redshift is 1100. From now onwards, CMBR temperature can be called as ‘Comic Black Hole’s Thermal Radiation’ temperature and can be expressed as ‘CBHTR’ temperature. Current cosmic black hole is growing at a rate of 14.66 km/sec in a decelerating mode. Uncertainty relation and all other microscopic physical constants play a crucial role in understanding the halt of the present cosmic expansion. In view of the confirmed zero rate of change in inverse of the Fine structure ratio (from the ground based laboratory experimental results), zero rate of change in the current CMBR temperature (from satellite data) and zero rate of change in the current Hubble’s constant (from satellite data), it can be suggested that, current cosmic expansion is almost all saturated and at present there is no significant cosmic acceleration.

Recent Advances on Electrically Induced Light Emission from Carbon Nanotubes

Light emission from individual (or small bundle) and network carbon transistors based on single-walled carbon nanotubes (SWNTs) and double-walled carbon nanotubes (DWNTs) is here reviewed in relation with the different mechanisms for light emission: electroluminescence [1,2,3] and incandescence or thermal radiation [4]. These studies guide our ongoing efforts towards making efficient light sources from nanotube emitters. The approach consists of operating the nanotubes transistors in different conditions of thermalisation and of exploring for each condition the different signatures in the emission, either thermal or electroluminescent, using an analysis of the resulting near-IR spectrum. The spectra were acquired in the energy range between 0.5 and 1.3 eV using the Spectrometer Infrared of Montreal (SIMON) mounted with a HgCdTe detector and on a probe station. Three different device configurations were measured. The first is a sub-monolayer network of nanotubes interconnected together to form a percolating semiconducting layer. [5] The numerous tube-tube junctions in the networks limit the current and prevent temperature raise by joule heating at higher bias. Electroluminescence from exciton recombination is found to dominate in all conditions, evidenced by well-defined emission peaks (~200meV in width) in the near-IR (Figure 1). The emission is ascribed to a radiative relaxation of the first excitonic transition. Even at very large biases, the main component of the emission from network transistors is electroluminescence, not incandescence. The second device geometry consists of a thick (~250 nm) and suspended carbon nanotube film having low resistance and reduced thermalization. This configuration favors joule heating when operating at large source-drain voltage and allows to significantly increase the nanotube temperature. The resulting incandescence was measured and used to calibrate SIMON for blackbody emission from a thermal source of pure nanotubes. A third set of devices was finally prepared with individual SWNT and DWNT transistors operating in vacuum, which conditions is used to prevent convection and for reducing the cooling capability of the substrate. The spectra were then compared with the different spectral signatures ascribed either to electroluminescence or thermal radiation depending on the biasing conditions. The experiments show a transition from electro-luminescence at low source-drain voltage to incandescence at higher voltage, with a regime of both in-between. These results will be discussed in terms of the dominant dissipation channels and carrier scatterings in nanotubes. Last, the best conditions to maximize light emission while avoiding heating and progress towards our effort to build electroluminescent transistors at 1,55 μm wavelength using sorted SWNTs will be discussed. Figure 1 Left: SEM and infrared micrographs of a large SWNT network transistor. Right: A carbon nanotube network transistor with the electroluminescence spectra at different biases. [Adapted from Ref. 5] REFERENCES [1] J. A. Misewich, R. Martel, Ph. Avouris, J. C. Tsang, S. Heinze, and J. Tersoff, Science, 300, 783 (2003). [2] J. Chen, V. Perebeinos, M. Freitag, J. Tsang, Q. Fu, J. Liu, and P. Avouris, Science, 310, 1171 (2005). [3] L. Marty, E. Adam, L. Albert, R. Doyon, D. Ménard and R. Martel, Phys. Rev. Lett. 96, 136803 (2006). [4] D. Mann, K. K., A. Kinkhabwala, E. Pop, J. Cao, X. Wang, L. Zhang, Q. Wang, J. Guo, and H. Dai, Nat. Nano, 2, 33 (2006). [5] E. Adam, C. M. Aguirre, L. Marty, B. C. St-Antoine, F. Meunier, P. Desjardins, D. Menard, and R. Martel, Nano Lett. 8, 2351 (2008).This work was done in collaboration with : Elyse Adam1, Pierre Lévesques2, Étienne Gaufrès2, Vincent Aymong2, David Ménard1 : RQMP and 1École Polytechnique de Montréal, Département de génie physique, Montréal, Québec H3C 3A7, Canada 2Université de Montréal, Département de chimie, Montréal, Québec H3T1J4, Canada.

The origin of white luminescence from silicon oxycarbide thin films

Silicon oxycarbide (SiCxOy) is a promising material for achieving strong room-temperature white luminescence. The present work investigated the mechanisms for light emission in the visible/ultraviolet range (1.5–4.0 eV) from chemical vapor deposited amorphous SiCxOythin films, using a combination of optical characterizations and electron paramagnetic resonance(EPR) measurements. Photoluminescence(PL) and EPR studies of samples, with and without post-deposition passivation in an oxygen and forming gas (H2 5 at. % and N2 95 at. %) ambient, ruled out typical structural defects in oxides, e.g., Si-related neutral oxygen vacancies or non-bridging oxygen hole centers, as the dominant mechanism for white luminescence from SiCxOy. The observed intense white luminescence (red, green, and blue emission) is believed to arise from the generation of photo-carriers by optical absorption through C-Si-O related electronic transitions,and the recombination of such carriers between bands and/or at band tail states. This assertion is based on the realization that the PL intensity dramatically increased at an excitation energy coinciding with the E04 band gaps of the material, as well as by the observed correlation between the Si-O-C bond density and the PLintensity. An additional mechanism for the existence of a blue component of the white emission is also discussed.

Basics of Black Hole Cosmology – First Critical Scientific Review

Considering 'black hole geometry' as the 'eternal cosmic geometry' and by assuming 'constant light speed rotation' throughout the cosmic evolution, at any time the currently believed cosmic 'critical density' can be shown to be the cosmic black hole's eternal 'volume density'. Thinking in this way and based on the Mach's principle, 'distance cosmic back ground' can be quantified in terms of 'Hubble volume' and 'Hubble mass'. To proceed further the observed cosmic redshift can be reinterpreted as an index of 'cosmological' light emission mechanism. By considering the characteristic mass unit

Fluorescent carbon nanomaterials: "quantum dots" or nanoclusters?

Despite many efforts, the mechanisms of light absorption and emission of small fluorescent carbon nanoparticles (C-dots) are still unresolved and are a subject of active discussion. In this work we address the question as to whether the fluorescence is a collective property of these nanoparticles or they are composed of assembled individual emitters. Selecting three types of C-dots with "violet", "blue" and "green" emissions and performing a detailed study of fluorescence intensity, lifetime and time-resolved anisotropy as a function of excitation and emission wavelengths together with the effect of viscogen and dynamic fluorescence quencher, we demonstrate that the C-dots represent assemblies of surface-exposed fluorophores. They behave as individual emitters, display electronic anisotropy, do not exchange their excited-state energies via homo-FRET and possibly display sub-nanosecond intra-particle mobility.

Cosmic Redshift, Temperature, Growth Rate and Age in Stoney Scale Black Hole Cosmology

Throughout the cosmic evolution, currently believed cosmic “critical density” can be shown to be a default result of the “positively curved” light speed rotating black hole universe “mass density”. As there is no observational or experimental evidence to Friedmann’s second assumption, the density classification scheme of Friedmann cosmology must be reviewed at fundamental level and possibly can be relinquished. With cosmic light speed rotation galactic rotational curves can be understood. The observed cosmic redshift can be reinterpreted as an index of “cosmological” thermodynamic light emission mechanism. Clearly speaking during cosmic evolution, at any time in the past, in hydrogen atom—emitted photon energy was always inversely proportional to the cosmic temperature. Thus past light emitted from older galaxy’s excited hydrogen atom will show redshift with reference to the current laboratory data. Note that there will be no change in the energy of the emitted photon during its journey from the distant galaxy to the observer. Past high cosmic temperature may be the root cause of observed super novae dimming. By considering the “Stoney mass” as the initial mass of the baby cosmic black hole, past and current physical and thermal parameters (like angular velocity, growth rate, age, redshift, thermal energy density and matter density) of the cosmic black hole can be understood. For a past cosmic temperature of 3000 K, obtained redshift is 1100. From now onwards, CMBR temperature can be called as “Comic Black Hole’s Thermal Radiation” temperature and can be expressed as “CBHTR” temperature. Current cosmic black hole is growing at a rate of 14.66 km/sec in a decelerating mode. In view of the confirmed zero rate of change, the current CMBR temperature (from satellite data) and zero rate of change in the current Hubble’s constant (from satellite data), it can be suggested that, current cosmic expansion is almost all saturated and at present there is no significant cosmic acceleration. From microscopic physics point of view, can be considered as a true index of future cosmic rate of expansion.

Studies on the Orientation of ACEL ZnS:Cu Particles in Applied AC Fields

In the last sixty years the understanding of the mechanisms of alternating current electroluminescence (ACEL) in transition metal-doped zinc sulfides, in particular ZnS:Cu particles has been the goal of all workers in the field. An in depth understanding of the crystallography and uncommon hemimorphic nature of these particles has lead to some understanding as to mechanism of light emission under an alternating current field. Hydrochloric acid etching of ZnS:Cu particles has allowed an intimate study of the hemimorphic nature and high density of planar stacking faults present in the particles that are critical for ACEL to occur. This work using complimentary field emission scanning electron microscopy and digital optical microscopy shows that the alignment of the planar stacking faults of these particles relative to the applied electric field is critical for light emission. Perpendicular alignment of the stacking faults results in no emission of light; as the alignment gradually approaches parallel emission increases and at parallel reaches a maximum. Thus, for devices using these materials alignment of the particles with the electric field is most important to maximize light output.

Influence of the ion synthesis and ion doping regimes on the effect of sensitization of erbium emission by silicon nanoclusters in silicon dioxide films

The photoluminescence spectra of erbium centers in SiO2 films with ion-synthesized silicon nanoclusters under nonresonant excitation were investigated. Erbium was introduced into thermal SiO2 films by ion implantation. The dependences of photoluminescence intensity on the dose, the order of ion implantation of Si and Er, the annealing temperature, and additional Ar+ and P+ ion irradiation regimes, i.e., factors determining the influence of radiation damage and doping on sensitization of erbium luminescence by silicon nanoclusters, were determined. It was found that the sensitization effect and its amplification due to doping with phosphorus are most pronounced under the conditions where nanoclusters are amorphous. The quenching of photoluminescence due to radiation damage in this case manifests itself to a lesser extent than for crystalline nanoclusters. The role of various factors in the observed regularities was discussed in the framework of the existing concepts of the mechanisms of light emission and energy exchange in the system of silicon nanoclusters and erbium centers.

Light Emission Induced by the Indium Distribution in InGaN Nanowires

The InGaN nanowires (NWs) have attracted intense attention for their huge potential in applications such as light emitting diodes, laser diodes and solar cells. Although lots of work are focused on improving their optical performance, little is known about the influence of the In distribution and the surface states on the microscopic light emission mechanism. In order to give an atomic level understanding, we investigate the electronic structures of the wurtziteGa-rich InGaN NWs with different In distributions using first-principles calculations. We find that the In-atoms are apt to distribute on the surface of the NWs and the short surface In-N chains can be easily formed. For the unsaturated NWs, several new bands are induced by the surface states, which can be modified by the surface In microstructures. The randomly formed surface In-N chains can highly localize the electrons/holes at the band edges and dominate the interband optical transition. For the saturated NWs, the band edges are determined by the inner atoms. Our work is useful to improve the performance of the InGaN NW-based optoelectronic devices.

Role of nanocrystalline ZnO coating on the stability of porous silicon formed on textured (1 0 0) Si

In this study, a colloid of nanocrystalline ZnO particles prepared by chemical route is sprayed on porous silicon layers. Porosity and thickness of PS layers were estimated by gravimetric analysis. Upon adsorption of ZnO colloids on PS films, oxidation of nanocrystalline Si causes shrinkage of the Si-core due to the breaking of SiSi bonds resulting in a blue-shift in PL spectra. The PL blue-shift can also be related to SiO species or due to defects and the silica networks on which OH groups are absorbed due to ZnO incorporation as also supported by our Fourier transform infrared (FTIR) and X-ray photoelectron (XPS) studies, respectively. From high resolution X-ray diffraction (HRXRD) studies, a better crystalline perfection and considerable reduction in stress/strain values were observed for PS/ZnO layers as compared to virgin PS layers. The changes in the chemical composition at the surface of PS upon adsorption of ZnO colloids as elucidated by FTIR and XPS studies could be responsible for different PL emission and lattice-mismatch characteristics. The improved stability properties of PS are attributed to the strong absorption/adsorption of ZnO into the highly porous vertical layers separating macroscopic domains of nanoporous silicon and the mechanism of light emission from PS/ZnO layers is discussed on the basis of proposed energy band gap diagram.

To confirm the existence of Black hole cosmology

It may be noted that, increased redshifts and increased distances forced Edwin Hubble to propose the Hubble’s law. In fact there is no chance or scope or place for 'galaxy receding'. If it is possible to show that, (from the observer) older galaxy’s distance increases with its ‘age’, then automatically the concepts ‘galaxy receding’ and ‘accelerating universe’ can be put for a revision at fundamental level. Its only our belief in its 'given' (Doppler shift based) unproven cosmological interpretation. Even then, merely by estimating galaxy distance and without measuring galaxy receding speed, one cannot verify its acceleration. Clearly speaking: two mistakes are happening here. 1) Assumed galaxy receding speed is not being measured and not being confirmed. 2) Without measuring and confirming the galaxy receding speed, how can one say and confirm that it (galaxy) is accelerating. It is really speculative and unfortunate also. During cosmic expansion, assuming past and present galaxies (which actually found to have gigantic structures) as ‘points’ and guessing photons coming from that galactic point particles seem to be ad-hoc. If light is coming from the atomic matter of the gigantic galaxy, then cosmic redshift can be interpreted as an index of the galactic atomic ‘light emission mechanism’. In no way it seems to be connected with ‘galaxy receding’. Whatever may be the expression, definitions of cosmic red shift seem to be ad-hoc and not absolute. Hence with redshift concept - one may not be able to understand the actual rate of cosmic expansion and actual cosmic geometry. Some cosmologists use the term ‘Hubble volume’ to refer to the volume of the observable universe. At any given time, the product of ‘critical density’ and ‘Hubble volume’ gives a characteristic cosmic mass and it can be called as the ‘Hubble mass’. Interesting thing is that, Schwarzschild radius of the Hubble mass again matches with the Hubble length. Most of the cosmologists believe that this is merely a coincidence. If one is able to show its applications in different areas of fundamental physics, certainly it can be given more significance and superiority compared to the mysterious ‘dark energy’. At any given cosmic time, ‘Hubble length’ can be considered as the gravitational or electromagnetic interaction range. Hubble volume and Hubble mass play a crucial role in quantum physics, nuclear physics, atomic physics and particle physics. If universe constitutes so many galaxies, if each galaxy constitutes a central fast growing and (light speed) spinning black hole and if black hole geometry is more intrinsic than its ‘mass’ and ‘mass density’, then considering universe as a ‘growing and light speed rotating black hole’ may not be far away from reality. By increasing the number of applications of Hubble mass and Hubble volume in other areas of fundamental physics, slowly and gradually and in a progressive way concepts of Black hole Cosmology can be strengthened and can also be confirmed. Unknowingly the fundamental physical laws are being developed, being executed and being proven inside and under the background of a growing and light speed rotating black hole universe. It can be suggested that, ‘quantum of angular momentum’ may be due to the cosmological manifestation and ‘discrete nature’ of angular momentum may be due the discrete nuclear matter. In any bound system, ‘operating force’ only plays major role in maintaining the ‘existence of the bound system’ and ‘angular momentum’ is one of the result. If one is able to make the operating force as discrete, then automatically one can observe a discrete structure like discrete radii, discrete angular momentum and discrete energy levels. Alternatively if atomic nucleus constitutes any fixed number of protons and any fixed number of neutrons, it is possible to guess that- nuclear mass is discrete. If nuclear matter is discrete, it is also possible to have a discrete atomic structure . In this new direction authors noticed some interesting and very strange coincidences. Main problem is that, the new relations are very simple to understand and very difficult to confirm. The most important point to be noted here is that, synthesis of elementary physical constants seem to be more fundamental than the ‘cosmological nucleosynthesis’.

Applications of Hubble Volume in Atomic Physics, Nuclear Physics, Particle Physics, Quantum Physics and Cosmic Physics

In this paper an attempt is made to emphasize the major shortcomings of standard cosmology. It can be suggested that, the current cosmological changes can be understood by studying the atom and the atomic nucleus through ground based experiments. If light is coming from the atoms of the gigantic galaxy, then redshift can be interpreted as an index of the galactic atomic ‘light emission mechanism’. In no way it seems to be connected with ‘galaxy receding’. With ‘cosmological increasing (emitted) photon energy’, observed cosmic redshift can be considered as a measure of the age difference between our galaxy and any observed galaxy. If it is possible to show that, (from the observer) older galaxy’s distance increases with its ‘age’, then ‘galaxy receding’ and ‘accelerating universe’ concepts can be put for a revision at fundamental level. At any given cosmic time, the product of ‘critical density’ and ‘Hubble volume’ gives a characteristic cosmic mass and it can be called as the ‘Hubble mass’. Interesting thing is that, Schwarzschild radius of the ‘Hubble mass’ again matches with the ‘Hubble length’. Most of the cosmologists believe that this is merely a coincidence. At any given cosmic time,’Hubble length’ can be considered as the gravitational or electromagnetic interaction range. If one is willing to think in this direction, by increasing the number of applications of Hubble mass and Hubble volume in other areas of fundamental physics like quantum physics, nuclear physics, atomic physics and particle physics - slowly and gradually - in a progressive way, concepts of ‘Black hole Cosmology’ can be strengthened and can also be confirmed.

Band Edge Modulation and Light Emission in InGaN Nanowires Due to the Surface State and Microscopic Indium Distribution

InGaN nanowires (NWs) show exceptional optical properties and have huge potential in applications such as light-emitting diodes, laser diodes, and solar cells. Although lots of work has focused on improving their optical performance, little is known about the influence of the In distribution and surface states on the microscopic light emission mechanism. In order to give an atomic-level understanding, we investigate the electronic structures of the wurtzite Ga-rich InGaN NWs with different In distributions using first-principles calculations, in which both the unsaturated and saturated NWs are considered. We find that In atoms are apt to distribute on the surface of the NWs and that the short surface In–N chains can be easily formed. For the unsaturated NWs, several new bands are induced by the surface states, which can be modified by the surface In microstructures. The randomly formed surface In–N chains can highly localize the electrons/holes at the band edges and dominate the interband optical transiti...

Nucleus, Atom and the Universe – a combined study

Now a days many astrophysicists suggest that every galaxy constitutes a central (growing and fast spinning) black hole. Really it is amazing. If the observable universe constitutes so many galaxies then considering universe as a growing and light speed rotating black hole may not be far away from reality. It may be noted that role of dark energy in understanding the unification of fundamental forces is very insignificant. At any given cosmic time, Hubble length can be considered as the gravitational or electromagnetic interaction range. If light is coming from the atomic matter of the galaxy, then the observed redshift can be interpreted as an index of the galactic atomic light emission mechanism. During cosmic evolution, as cosmic time increases, hydrogen atom emit photons with increased quanta of energy and thus past light quanta emitted from an old galaxy will have less energy and show a red shift with reference to our galaxy. During its journey light quanta will not lose energy and there will be no change in the lights wavelength. In this way without any difficulty the accelerating universe concept can be eliminated and a decelerating universe concept can be retained. To understand this light emission mechanism and to move further it is possible to consider the characteristic nuclear radius and characteristic angular momentum of the revolving electron as cosmological time oriented physical variables. Note that, in any bound system, operating force only plays major role in maintaining the existence of the bound system and angular momentum is one of the result. If one is able to make the operating force as discrete, then automatically one can observe a discrete structure like discrete radii, discrete angular momentum and discrete energy levels. With reference to the classical force limit \(\frac{c^4}{G}\) and considering Avogadro number $N$ as a large and discrete proportionality ratio, a characteristic discrete imaginary electroweak force magnitude can be defined as \(\frac{c^4}{G}\)/\(\left(n.N\right)^2\) where n =1,2,3,..

Photoluminescence of Cu:ZnS, Ag:ZnS, and Au:ZnS nanoparticles applied in Bio-LED

In this work, transition elements, including Cu2+, Ag+, and Au3+, were used to dope in zinc sulfide (ZnS) by chemical solution synthesis to prepare Cu:ZnS, Ag:ZnS, and Au:ZnS nanoparticles, respectively. Transition elements doping ZnS nanoparticles form the electronic energy level between the conduction band and valance band, which will result in the green light emission. There is a zinc sulfide emission shift from blue (~3.01 eV) to green light (~2.15 eV). We also found that Au:ZnS nanoparticles will emit a green light (~2.3 eV) and a blue light (~2.92 eV) at the same time because the mechanism of blue light emission was not broken after Au element had been doped. Furthermore, we used sodium chlorophyllin copper salt to simulate chlorophyll in biological light emission devices (Bio-LED). We combined copper chlorophyll with Cu:ZnS, Ag:ZnS, and Au:ZnS nanoparticles by a self-assembly method. Then, we measured its photoluminescence spectroscopy and X-ray photoelectron spectroscopy to study its emission spectrum and bonding mode. We found that Au:ZnS nanoparticles are able to emit green and blue light to excite the red light emission of copper chlorophyll, which is a potential application of Bio-LED.

Surface Plasmon-Enhanced Light-Emission Mechanism of Ag-Coated ZnO/Al2O3 Core/Shell Nanorod Structures

Surface plasmon (SP)-enhanced light emission mechanism has been investigated for the Ag-coated ZnO/Al2O3 core/shell nanorods (NRs). Structural characterizations showed that the ZnO NRs were covered by conformal Al2O3 layer and coated by Ag nanoparticles (NPs). The optical studies by photoluminescence (PL) showed abnormal variation of PL intensity with increasing the thickness of Al2O3. For the Ag NPs-coated ZnO NRs without Al2O3 shell layer, the PL emission quenched due to direct transfer of the photo-excited electrical carriers from ZnO NRs to Ag NPs. With thin Al2O3 layers less than 15 nm, the PL intensity increased with increasing the thickness of Al2O3 layers due to weakening of the Förster-type energy transfer while strong SP-mediated PL emission enhancement. For thicker Al2O3 layers than 15 nm, however, the PL intensity decreased with increasing the thickness of Al2O3 layers due to weakening of SP-mediated PL emission enhancement.

Tunable red light emission from a-Si:H/a-SiN_x multilayers

A tunable red photoluminescence from a-Si:H/a-SiNx multilayers was modulated in the wavelength range of 800–640 nm by controlling the thickness of the a-Si:H sublayer from 4 to 1.5 nm. Subsequent annealing was used to improve red photoluminescence without recrystallization of the amorphous silicon sublayers. The significant enhancement of red emission was found to depend on the decomposition of the Si–H bond in a-Si:H sublayers. Based on the absorption measurement, Raman, and FTIR spectra, the origin of light emission is ascribed to the silicon dangling bonds associated with hydrogen in a-Si:H sublayers, and the mechanism of light emission is suggested from the radiative recombination between the electrons existing at the negatively charged levels of silicon dangling bond and holes at the valence band.