Evaporation Power Research Articles

Combinatorial screening of halide perovskite thin films and solar cells by mask-defined IR laser molecular beam epitaxy

As an extension of combinatorial molecular layer epitaxy via ablation of perovskite oxides by a pulsed excimer laser, we have developed a laser molecular beam epitaxy (MBE) system for parallel integration of nano-scaled thin films of organic–inorganic hybrid materials. A pulsed infrared (IR) semiconductor laser was adopted for thermal evaporation of organic halide (A-site: CH3NH3I) and inorganic halide (B-site: PbI2) powder targets to deposit repeated A/B bilayer films where the thickness of each layer was controlled on molecular layer scale by programming the evaporation IR laser pulse number, length, or power. The layer thickness was monitored with an in situ quartz crystal microbalance and calibrated against ex situ stylus profilometer measurements. A computer-controlled movable mask system enabled the deposition of combinatorial thin film libraries, where each library contains a vertically homogeneous film with spatially programmable A- and B-layer thicknesses. On the composition gradient film, a hole transport Spiro-OMeTAD layer was spin-coated and dried followed by the vacuum evaporation of Ag electrodes to form the solar cell. The preliminary cell performance was evaluated by measuring I-V characteristics at seven different positions on the 12.5 mm × 12.5 mm combinatorial library sample with seven 2 mm × 4 mm slits under a solar simulator irradiation. The combinatorial solar cell library clearly demonstrated that the energy conversion efficiency sharply changes from nearly zero to 10.2% as a function of the illumination area in the library. The exploration of deposition parameters for obtaining optimum performance could thus be greatly accelerated. Since the thickness ratio of PbI2 and CH3NH3I can be freely chosen along the shadow mask movement, these experiments show the potential of this system for high-throughput screening of optimum chemical composition in the binary film library and application to halide perovskite solar cell.

A novel adsorption module with fiber heat exchangers: Performance analysis based on driving temperature differences

A main focus of recent R&D on adsorption modules for thermally driven heat pumps and chillers has been to enhance the volume specific power output while maintaining a reasonable coefficient of performance (COP).An adsorption module using a new type of heat exchanger based on aluminum sintered metal fiber structures brazed on flat fluid channels has been developed. The heat exchangers for adsorber/desorber and evaporator/condenser are identically constructed. The adsorption heat exchanger is coated with a silico-alumino phosphate (SAPO-34) by a partial support transformation direct crystallization (PST) [1]. Both components are placed in a vacuum tight housing using a valve-free configuration. Water is used as adsorptive.The experimental characterization of the module shows a high volume specific power (up to 82 W/litre module for cooling, 320 W/litre for heating). Although no heat is recovered between ad- and desorption cycle, a COP of almost 0.4 is reached for cooling and 1.4 for heating.Driving temperature differences are defined for the analysis of the heat exchanger performance. The evaporator/condenser shows extremely good performance with about 240 W/K specific evaporation power per litre of heat exchanger, while the adsorber is limiting the module performance.

Contact Resistivity of Evaporated Al Contacts for Silicon Solar Cells

The contact resistivity of evaporated Al on doped silicon is examined for a range of process conditions common to the fabrication of laboratory silicon solar cells. The effects of silicon surface preparation prior to evaporation, sintering temperature, the use of a shutter, and evaporation power are investigated. The presented evaporation conditions yielded the lowest published contact resistivity between Al- and phosphorus-doped Si over a large range of doping concentration. It is also demonstrated that a contact resistivity below 10−6 Ω·cm 2 can be achieved without sintering. Three-dimensional simulations are utilized to compare the obtained results for evaporated Al contacts with those for passivated contacts.

A physical model of an ejection suppressed CPS liquid lithium divertor target

A physical model has been developed which includes high temperature liquid lithium evaporation, the expanding motion of the liquid lithium vapour cloud, the shielding effects of the vapour cloud on incident plasma particle bombardments, ejection suppressed analysis and a perpendicular field proposal, and photon radiation, heat flux and transport in the lithium vapour cloud plasma. The engineering outline design scheme and the relevant parameters for the liquid lithium surface divertor target plate configured by discrete tiny capillary arrays have been established. Splashing can be suppressed by utilizing discrete and electrical insulating capillary porous systems (CPSs), since the conductivity among the capillary cells has been cut off by adopting a special kind of ceramic composite material made of a non-conducting and unbreakable composite which is able to withstand high temperatures. The formula to describe the temperature-dependent evaporation power has been derived. The maximum temperature increases of the discrete plasma-facing liquid lithium surface divertor target plate have been compared under the high energy flux deposition of 10 MJ m−2 during a 1 ms time duration with or without evaporation power. The results show that a high surface heat load can be withstood by the designed discrete plasma-facing liquid lithium surface divertor target plate due to violent evaporation. The energy deposition of incident energetic particles and weakly relativistic electrons from the scrape-off layer have been calculated. A laboratory experimental facility to simulate liquid lithium surface interactions with plasma has been set up. Research on lithium evaporation, re-deposition and ejection suppressed experiments under high density linear plasma dumping is ongoing.

A thermoeconomic model of a photovoltaic heat pump

In this paper the model of a heat pump whose evaporator operates as a photovoltaic collector, is studied. The energy balance equations have been used for some heat pump components, and for each layer of the photovoltaic evaporator: covering glaze, photovoltaic modules, thermal absorber plate, refrigerant tube and insulator. The model has been solved by means of a program using proper simplifications. The system input is represented by the solar radiation intensity and the environment temperature, that influence the output electric power of the photovoltaic modules and the evaporation power. The model results have been obtained referring to the photovoltaic evaporator and the plant operating as heat pump, in terms of the photovoltaic evaporator layers temperatures, the refrigerant fluid properties values in the cycle fundamental points, the thermal and mechanical powers, the efficiencies that characterize the plant performances from the energy, exergy and economic point of view. This study allows to realize a thermoeconomic comparison between a photovoltaic heat pump and a traditional heat pump under the same working conditions.

Experimental Investigation of the Reflectivity of Refractory Dielectric Materials in the Vacuum Ultraviolet Spectral Region

The paper deals with the results of experimental investigation of spectrally averaged group reflectivities R(Δλ) in a vacuum ultraviolet (hν ∼ 10 to 70 eV) spectral range of commercial samples of high-temperature dielectric materials (α-Al2O3, SiO2, BNC) under conditions of a prethreshold (prior to the beginning of developed surface evaporation) power density of probing radiation.

P-Type Doping of Cubic GaN by Carbon

Successful p-type doping of cubic GaN epilayers by carbon using an e-beam evaporation source is reported. At room temperature Hall-effect measurements of the C-doped cubic GaN epilayer gave hole concentrations and hole mobilities as high as 6 x 10 17 cm -3 and 200 cm 2 /Vs, respectively. The thermal activation energy of the C-acceptor is (215 ± 10) meV. Low temperature photoluminescence spectra show a new line appearing at 3.08 eV. The emission energy increases with increasing e-beam evaporation power. This 3.08 eV line is attributed to a C related donor acceptor (D 0 A 0 ) transition.

P-Type Doping of Cubic GaN by Carbon

Successful p-type doping of cubic GaN epilayers by carbon using an e-beam evaporation source is reported. At room temperature Hall-effect measurements of the C-doped cubic GaN epilayer gave hole concentrations and hole mobilities as high as 6 x 10 17 cm -3 and 200 cm 2 /Vs, respectively. The thermal activation energy of the C-acceptor is (215 ± 10) meV. Low temperature photoluminescence spectra show a new line appearing at 3.08 eV. The emission energy increases with increasing e-beam evaporation power. This 3.08 eV line is attributed to a C related donor acceptor (D 0 A 0 ) transition.

Carbon - an alternative acceptor for cubic GaN

Carbon doping of cubic GaN epilayers has been performed by rf-plasma-assistedmolecular beam epitaxy using an e-beam evaporation source. Hall-effectmeasurements at room temperature and low-temperature photoluminescence wereused to characterize the electrical and optical properties. Room-temperatureHall-effect measurements revealed a maximum hole concentration of the c-GaNepilayer of 6×1017 cm-3 with a mobility of 200 cm2 V-1 s-1. With increasing e-beam evaporation power anew photoluminescence line at 3.08 eV appeared at 2 K. This line is attributedto a donor acceptor transition, which involves the shallow CN acceptor.From the spectral position the binding energy of the C acceptor is estimatedto be about EC = 0.215 eV. At high C concentrations a deep band appeared at2.1 eV indicating compensation effects.

Preparation of thin films of the ternary heavy fermion system CeNi 2 Ge 2

Ge2 layers on W(110). In order to produce well-ordered and atomically clean surfaces of the Ce-based intermetallic system the growth was performed under UHV conditions (p<2×10-11 mbar). Both the polycrystalline CeNi2Ge2 compound and the individual elements Ce, Ni, and Ge were used as evaporants. The characterisation of the layers was made with LEED, SEM, and XPS. We find a significant influence of the substrate temperature and the evaporation power on the growth characteristics. The compound material CeNi2Ge2 exhibits complicated behaviour when evaporated. Under carefully selected growth conditions we obtain well-ordered films with a stoichiometry of Ce:Ni:Ge=1:2:2 and a (001) oriented surface of the body-centered tetragonal ThCr2Si2-type structure. The k∥ dispersion and binding energies of the valence bands of these layers were determined with ARUPS.

Electron beam evaporation with hot filament and magnetic field—Computer control and parameter estimation

Electron beam evaporators with magnetic field and hot filament are widely used in vacuum technology. The lack of adequate models for the electron beam evaporating process makes it difficult to predict the optimum parameters for quality and low cost process control. A mathematical model for transforming the filament heating power into evaporation power is developed. A discrete model for computer control and an algorithm for the model's parameter estimation are presented.

On the power control of evaporation sources with hot filament and magnetic beam deflection

An efficient regulator for evaporation power is described. The combination of cheaply available components makes this analogue control unit versatile and inexpensive. The regulator is well suited for different applications such as electron bombardment heating, ion beam and thermoemission process control.

Abstract: Dynamic control of the vacuum deposition of optically effective thin films

The control of the deposition of optically effective thin films by optical measurements was in the past often restricted to the evaluation of static measurements of the optical parameters (reflection and transmission) of thin films for the generation of a cutoff signal for the deposition. This cutoff condition was at a later date obtained by differentiation of the optical signal with respect to time. We have expanded this method to obtain rate control during the entire deposition and achieve cutoff at different than quarter wave thickness. Furthermore, we have made the system ’’self−learning’’ so that the optimized evaporation power level of each deposition cycle is used to start the next cycle under near optimum conditions. The results which can be achieved in large scale production with this method will be dicussed.

Evaporation characteristics of materials from an electron beam gun II

The evaporation characteristics of Al2O3, As, B, Ba, BaCl2, BaF2, Be, BeO, Bi, B4C, Ca, CaF2, Cd, CdS, Co, Dy, Eu, Gd, Ge, In, Ir, KCl, KF, La, LaB6, Li, LiF, Mn, NaCl, NaF, Nd, Pd, Pt, Pr, Rh, Sc, Se, Sb, Sb2O3, Sr, S8, Ti, V, WO3, Yb, Y2O3, Zr, ZrO2 from an electron beam source are described. In addition, similar, previously published measurements of Ag, Al, Al2O3, Au, C, Cr, Fe, Inconel, Mo, Mg, MgF2, Nb, Ni, Pb, Si, SiO, SiO2, Sn, Ta, TiOx, W, and Zn have been expanded. The nonquantitative characteristics, melt type, stability, and tendency to spit, are reported, in addition to the evaporation rate, power, and pressure.

Direct contact vapor recompression evaporation desalination process economic assessment

Recent data on the direct transfer of heat across a liquid-liquid interface during vaporization and condensation have made it possible to estimate the cost of producing potable water by direct contact vapor recompression evaporation of sea water. The advantages of direct contact heat exchange are: (a) eliminates costly heat transfer surfaces, (b) prevents scale formation, (c) prevents corrosion, (d) allows a high rate of heat transfer, (e) allows close temperature approach, and (f) simplifies the evaporator design. These advantages show up as both capital and operating cost reductions compared to the costs of the standard vapor recompression process. As with the standard process added advantages could be obtained by combining the direct contact process with multi-effect evaporation or nuclear power production. The proportional savings should be about the same as are now proposed for the standard process.

Effects of Climatic Factors on Fruit Volume Increase and Leaf Water Deficit of Citrus in Relation to Soil Suction

AbstractThe primary factors affecting the rate of fruit volume increase and leaf water deficit of navel orange trees were investigated under two irrigation treatments. One treatment was applied when tensiometers in the major root zone indicated 20 cbar soil suction and the other treatment was applied at 100 cbar soil suction. The correlations between either fruit volume increase or leaf water deficit and various environmental conditions were studied by factor analysis to determine possible primary factors affecting the water status of the trees. Soil suction, a primary factor in both treatments, influenced the fruit and the leaf in only the 100 cbar treatment. Rate of water movement through the soil to the plant roots could be the underlying factor. Another factor, evaporation power of the atmosphere during high diurnal transpiration affected the rate of fruit volume increase in only the 100 cbar treatment.

Ecophysiological significance of the height gradient of the equivalent evaporation power of the atmosphere

The term “equivalent evaporation power” is suggested to denote the evaporation power of the atmosphere measured as the relative evaporation from an evaporimeter which resembles to a great extent the physical conditions occurring during transpiration of a plant leaf (e.g. the Piche evaporimeter). The height dependence of equivalent evaporation power at heights between 5 and 500 cm. in an “open area”, in a field of sugar beet, maize, in a mature deciduous wood, in its small circular rejuvenation clearing and on a great clearing was investigated. The higher the absolute values of evaporation the lower the height gradient which is obviously observed to decrease progressively with height in all cases (Figs. 1 and 2). The stands decrease the average equivalent evaporation power in the height interval exceeding their height. Differences between the relative values of equivalent evaporation power of atmospheric environment surrounding different leaves of one plant are frequently considerably higher than those between ecoclimatically completely distinct localities (e.g. between a forest stand and a clearing). A statistically significant positive correlation was found to exist between the gravimetrically determined all-day total of transpiration of seedlings ofFagus silvatica L. andAcer platanoides L., freely exposed in small lysimeters for the entire vegetation season and between the all-day total of equivalent evaporation power. For the number of days n=95 the mean correlation coefficient r was +0·58±3.0·031 for the beech and +0·56±3.0·046 for the maple. The regression coefficient, which is linearly proportional to the leaf area, was low and provides evidence for the biological regulation of transpiration. It was shown by simultaneous measurements of transpiration (gravimetrically) of leaves ofSyringa vulgaris L. (n=95) and of equivalent evaporation power at the height of 10, 50 and 150 cm. above the ground in an “open area” that the height gradient of equivalent evaporation power of the atmosphere under natural conditions affects the intensity of transpiration at different heights (Fig. 3). The observed facts are undoubtedly to be associated with the formation of the xerophytic or mesophytic character of leaves located at different levels of the same plant, and thus withZalensky’s law.

Analysis of Electrode Phenomena in the High-Current Arc

An analysis is made of the phenomena at the electrodes of a high-current short-time arc. It is shown that the input power density to the anode spot is in the range 5×104 to 1×106 watts/cm2. To a first-order approximation, all this power can be carried off by evaporation. Power conducted into the metal and lost by radiation is negligible in the probable operating range. For most materials, the anode spot is probably considerably above the boiling temperature. The process of evaporation holds the spot temperature constant at a value such that the input power and evaporation power are equal. Experimental data indicate that for any given metal the anode spot temperature is that for which the evaporation power density is at least 3×105 watts/cm2. As an example, for copper the theoretical limits of temperature are 2490 to 3040°K, while experimental data indicate a temperature of 2920°K. Other metals considered are: Ag, Al, C, Fe, Mo, Sn, Ti, W, Zn, Zr. It is also shown that for the maximum power input that can be expected at the cathode, the thermionic emission current density is very small compared to the observed values of current density.

A Preliminary Inquiry into the Significance of Tracheid-Caliber in Coniferae

1. There is considerable evidence that the width of the spring tracheids in evergreen Coniferae is largely decided by two factors, systematic affinity and available water supply. So far as the latter is concerned, the spring tracheids are generally narrowest in species of xerophilous habitat. 2. In American species of Pinus belonging to section I (Haploxylon), variation in the width of the spring tracheids runs quite parallel with difference of systematic affinity and of available water supply (including influences promoting transpiration). Thus the first step in the evolution of this section of Pinus would appear to have been a division into a more xerophilous type (ancestral Paracembra), and a less xerophilous type (ancestral Cembra), and each of these subsections would appear to have undergone similar division into more or less xerophilous groups, that is, into Parrya and Balfouria, also Eu-cembra and Strobus. The two East Indian species, P. Gerardiana and P. excelsa, structurally accord with this theory. 3. Among American species of Pinus belonging to section II (Diploxylon), those with narrow spring tracheids are more xerophilous in distribution, while those with the widest tracheids belong to a subtropical or tropical moist climate. Though in general this section of Pinus supports the theory given in paragraph 1, there are in it certain species in which width of tracheid does not appear to correspond with the supply of available water. Such discrepancies, whether real or only apparent, may be due to one or more of the intervening causes mentioned in paragraph 6. 4. Species of other North American genera of evergreen Coniferae show differences in the width of spring tracheids that may possibly be partly due to differences in affinity; as species of the same habitat, but belonging to different genera, may differ considerably in tracheid width, or, on the other hand, may approximate to agreement. Some of these genera, namely, Torreya, Chamaecyparis, Sequoia, and Juniperus, support the view that the width of the spring tracheid is correlated with available water supply; somewhat favoring the view are Cupressus and Picea; indifferent in indication are Abies and Larix. 5. The theory here propounded derives support from measurements of the width of the spring vessels of American deciduous species of Quercus. For narrowness and wideness of spring vessels in the main are respectively associated with scantiness and abundance of water supply. But in the same kind of habitat the deciduous black oaks would seem to have narrower spring vessels than are possessed by the deciduous white oaks. 6. Though the evidence as a whole strongly favors the theory here propounded, much fuller information is necessary before a safe conclusion may be drawn. Hence this inquiry and the suggestions here given must be regarded as tentative and issued in the hope of stimulating inquiry in regard to factors that may intervene, such for instance as the following: climate (including evaporation power), exact soil water-content, level of water-table, etc., that form the environment of the different species of conifers; also, depth of root, duration of foliage and size of aggregate leaf surface, rate of transpiration, width of sap wood, etc., in the different species; also, variations within one and the same species in regard to the features just mentioned, as well as in the width of the spring tracheids, in different habitats.