Silicon photon spectrum

Figure 7 shows the photon spectrum from Cs and sources. They were obtained with a 1 cm pure Csl crystal at 117 K coupled to the photodiode with optical silicon grease. The light output was 26,000 photons/MeV, leading to an r.m.s energy resolution of less than 6 % for 511 keV photons. To our knowledge such a performance as not been achieved so far. 

Chhablani et al. showed that in oxidized PSi covalently loaded daunorubicin demonstrated sustained intravitreal release for 3 months without any evidence of toxicity, while physisorbed daunorubicin was released within 2 weeks and localized retinal toxicity were observed due to high daunorubicin concentration. Wu et al. added a new functionality to PSi dmg delivery system (Wu et al. 2011). They used 1-dimensional porous silicon photonic crystal in intravitreal delivery. The reflectance spectrum of the crystal (i.e., color) changed from red to green as daunombicin was releasing enabling real-time monitoring of the drag release proeess. These types of multifunctional delivery systems based on versatile properties of PSi are expeeted to be published much more in future. 

Kim H-J, Kim Y-Y, Lee K-W (2010) Multiparametric sensor based on DBR porous silicon for detection of ethanol gas. Curr Appl Phys 10 181-183 Kim H-J, Kim Y-Y, Lee K-W (2011) Sensing characteristics of the organic vapors according to the reflectance spectrum in the porous silicon multilayer structure. Sens Actuators A 165 276-279 King BH, Ruminski AM, Snyder JL, Sailor MJ (2007) Optical-fiber-mounted porous silicon photonic crystals for sensing organic vapor breakthrough in activated carbon. Adv Mater 19 4530 534... 

The short penetration depth of UV/blue photons is the reason that frontside CCD detectors have very poor QE at the blue end of the spectrum. The frontside of a CCD is the side upon which the polysilicon wires that control charge collection and transfer are deposited. These wires are 0.25 to 0.5 /xm thick and will absorb all UV/blue photons before these photons reach the photosensitive volume of the CCD. For good UV/blue sensitivity, a silicon detector must allow the direct penetration of photons into the photosensitive volume. This is achieved by turning the CCD over and thinning the backside until the photosensitive region (the epitaxial layer) is exposed to incoming radiation. 

Figures 6 and 7 show the absorption spectra of colloidal CdS and ZnS at various times of illumination. The two colloids were prepared by adding an NaSH solution to solutions of Cd(C10j2 or Zn(C104)2, respectively, colloidal silicon dioxide (commercially available from Dupont Ludox HS30) being present at 6 x 10 M as stabilizer in both cases. The absorption starts in both cases close to the wavelengths that correspond to the photon energies (515 nm or 2.4 eV for CdS 340 nm or 3.7 eV for ZnS) at which the absorptions begin in the macrocrystalline materials. It is seen that illumination causes not only a decrease in the intensity of the absorption spectrum but also a change in the shape of the spectrum. The onset of light absorption is shifted towards...

Sunlight is composed of photons with energy corresponding to the range of wavelengths within the solar spectrum. When photons strike the collector cell, they may be reflected, pass through, or be absorbed, but only the absorbed photons generate electricity. This is because the construction material (the silicon atoms in the crystal) has to receive 1.1 eV to cause its valence electron (electron in the outermost shell) to move into the conduction zone. 

This wavelength falls in the infrared region of the spectrum. Photons with shorter wavelengths (for example, visible light) carry more than enough energy to excite electrons to the conduction band in silicon. 

These multichannel detectors work by having hundreds of silicon photodiodes positioned side by side on a single collision crystal or chip. Each photodiode has an associated storage capacitor that collects and integrates the photocurrent generated when the photons strike the photodiode. Periodically, they are discharged and the current read. A spectrum cau be recorded if radiation dispersed into its different wavelengths falls on the surface of the diode array. 

Photoluminescence excitation (PLE) spectroscopy was carried out at 77K on oxidized porous silicon containing iron/erbium oxide clusters. The novel PLE spectrum of the 1535 nm Er PL band comprises a broad band extending from 350 to 570 nm and very week bands located at 640, 840, and 895 nm. The excitation at wavelengths of 400 - 560 nm was shown to be the most effective. No resonant PLE peaks related to the direct optical excitation of Er by absorption of pump photons were observed. The lack of the direct optical excitation indicates conclusively that Er is in the bound state and may be excited by the energy transfer within the clusters. 

There have been a few reports of II-VI and III-V heterojunction devices which have approached or even surpassed the performance of silicon cells. p-InP/n-CdS cells with a solar conversion efficiency of 12.5% have been fabricated.84 This good efficiency arises firstly because of the nature of InP the band gap is at 1.34 eV, which is optimal for the solar spectrum, and the transition is direct, so the absorption edge is steep. Secondly, there is an excellent crystal lattice match between InP and CdS, which means that almost fault-free junctions can be grown. p-CuInSe2/n-CdS cells which display current efficiencies (defined as electrons flowing in the short-circuit current per photon absorbed) of up to 70% between 550 and 1250 nm, and solar conversion efficiencies of ca. 5% have been made.85 p-CdTe/n-CdS cells of rather similar performance (current efficiency 85%, solar conversion efficiency 4.0%) have been produced without detailed attention to optimization of cell design, and it has been calculated that p-CdTe/n-ZiiaCdi-aS cells should be capable of a 41 44... 

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