Diethylselenide Research Articles

ФАЗОВА РІВНОВАГА ПАРА–РІДИНА РОЗЧИНІВ ДИЕТИЛСЕЛЕНУ ТА ДИЕТИЛЦИНКУ

Using a semi-empirical Wilson’s model, the vapor-liquid equilibrium in the “diethylzinc - diethyl selenide” system is described: the activity coefficients of the solution components, the separation coefficient, the excess functions of the solution (HE, GE, TSE) are calculated, and isothermal P-X diagrams are obtained. The parameters of the Wilson’s model were calculated on the basis of our data on measuring the temperature dependence for saturated vapor pressure of high-purity samples of diethylzinc, diethyl selenide and their equimolecular solution using iterations from the mathematical software package Mathsad 14. Peculiarities of intermolecular interaction in the “diethylzinc – diethyl selenide” system and the presence of a negative deviation from Raoul's law have been found. The studied system is homogeneous in the whole concentration range. The concentration dependence of the enthalpy of mixing is alternating for the researched temperature range (280-340 K).

Organoselenium Precursors for Atomic Layer Deposition.

Organoselenium compounds with perspective application as Se precursors for atomic layer deposition have been reviewed. The originally limited portfolio of available Se precursors such as H2Se and diethyl(di)selenide has recently been extended by bis(trialkylsilyl)selenides, bis(trialkylstannyl)selenides, cyclic selenides, and tetrakis(N,N-dimethyldithiocarbamate)selenium. Their structural aspects, property tuning, fundamental properties, and preparations are discussed. It turned out that symmetric four- and six-membered cyclic silyl selenides possess well-balanced reactivity/stability, facile and cost-effective synthesis starting from inexpensive and readily available chlorosilanes, improved resistance toward air and moisture, easy handling, sufficient volatility, thermal resistance, and complete gas-to-solid phase exchange reaction with MoCl5, affording MoSe2 nanostructures. These properties make them the most promising Se precursor developed for atomic layer deposition so far.

Influence of source transport rate upon fractions of Mg and Se in Zn1‐xMgxSeyTe1–y layers grown by metalorganic vapor phase epitaxy

AbstractThe growth of undoped Zn1–xMgx Sey Te1–y layers on (100) ZnTe substrates by metalorganic vapor phase epitaxy has been carried out. The fractions of Mg and Se, Raman property and surface roughness have been characterized as a function of bis‐methylcyclopentadienyl‐magnesium ((MeCp)2Mg) or diethylselenide (DESe) transport rates. It has been demonstrated that the Mg and Se fractions in Zn1–xMgx Sey Te1–y layer can be controlled successfully by these source transport rates. Furthermore, the behaviors of two Raman peaks related to ZnSeTe‐like longitudinal optical phonon mode and MgSeTe‐like one have been clarified for some Mg and Se fractions in Zn1–xMgx Sey Te1–y layers. It has been shown by varying (MeCp)2Mg or DESe transport rates that Zn1‐xMgx Sey Te1–y layer nearly‐lattice‐matched to ZnTe substrate shows low surface roughness. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Analysis of selenization in supercritical ethanol for the production of compound semiconductor films

Selenization is an essential reaction for the production of the metal selenide absorption layer in compound semiconductor thin-film solar cells. Application of supercritical ethanol facilitates the conversion from a Cu–In film to a CuInSe2 film at a low temperature of 300°C. In this study, we investigate the contribution of supercritical alcohols to the selenization reaction by employing some kinds of supercritical alcohol media with different reduction powers. We found that the high reduction power of ethanol is necessary for selenization without excess selenium deposition at low temperature. Moreover, 1H NMR analysis revealed that at supercritical conditions, decomposition of diethyl selenide occurs and reactive selenium species with a short lifetime at process temperatures dictate the selenization reaction, whereas stable selenium species prevent the deposition of excess selenium.

Growth Conditions and Structural Properties of Cu(In,Ga)Se2 Thin Films Prepared by Selenization Method Using Diethylselenide

The relationship between the selenization conditions and structural properties of Cu(In,Ga)Se2 (CIGS) thin films was investigated for the selenization method using diethylselenide (DESe). The grain structure changed markedly depending on selenization temperature, selenization time, and DESe flow rate. The CIGS thin films selenized at a high temperature (HT: 500–540 °C), which is referred to as a one-step selenization are very rough. On the other hand, the films selenized at a low temperature (LT: 350–450 °C) exhibited a relatively uniform thickness and densely packed grains, although they contain second binary phases such as In–Se and Cu9Ga4. To form a single-phase chalcopyrite CIGS film, a two-step selenization method is examined, in which the films selenized at LT (first step) are subsequently selenized at HT (second step). Single-phase densely packed CIGS thin films with uniform thickness were obtained by the two-step selenization. The use of the InSe/Cu0.7Ga0.3 precursor was proposed, and the selenization of this precursor successfully yielded single-phase CIGS thin films with a flat surface. The importance of the role of InSe during the selenization process using DESe is discussed.

Control of Grain in Cu(In,Ga)Se2 Thin Films Prepared by Selenization Method Using Diethylselenide

The relationship between the selenization condition and the grain structure has been studied. A single-phase chalcopyrite Cu(In,Ga)Se2 thin film with densely-packed grains and large grains have been prepared by the two-step selenization of the In/Cu–Ga bilayer precursor using diethylselenide (DESe). The formation of the In–Se compound in the early stage of the first-step selenization (T=350–450 °C) has been found to be important. The succeeding second-step selenization at high temperature of 540 °C led to the well developed (112) grain formation. The relationship between the selenization condition and the CIGS film structure is discussed with relation to the selenization mechanism.

Control of Grain in Cu(In,Ga)Se2Thin Films Prepared by Selenization Method Using Diethylselenide

The relationship between the selenization condition and the grain structure has been studied. A single-phase chalcopyrite Cu(In,Ga)Se2 thin film with densely-packed grains and large grains have been prepared by the two-step selenization of the In/Cu–Ga bilayer precursor using diethylselenide (DESe). The formation of the In–Se compound in the early stage of the first-step selenization (T=350–450 °C) has been found to be important. The succeeding second-step selenization at high temperature of 540 °C led to the well developed (112) grain formation. The relationship between the selenization condition and the CIGS film structure is discussed with relation to the selenization mechanism.

Selenization of Cu-In-Ga Metal Precursor Using DESe(Diethyl Selenide)

In this study, Cu(In,Ga)Se2 thin films were prepared using a Cu-In-Ga metallic precursor and diethylselenide (DESe) vapor. The Cu/(In+Ga) ratio of the precursor was adjusted by modulating the power impressed on the CuGa target. The Cu/(In+Ga) ratio was varied from 0.45 to 1.02, and the prepared precursors were selenized in a 500°C quartz furnace using DESe. The results showed that the preferred crystal phase and the uniformity of the thin film differed according to the composition of the precursor. After selenization, changes in grain size stemming from Cu composition were observed, and the occurrence of a binary phase was verified through KCN etching. Shifts in the Cu11(InGa)9 peak and the separation of CIS and CGS peaks relative to increased Ga content were also observed.

Morphological and Structural Changes in Cu(In,Ga)Se2 Thin Films by Selenization Using Diethylselenide

The morphological and structural changes in Cu(In,Ga)Se2 (CIGS) thin films during selenization using diethylselenide (DESe) are investigated. The surface morphology and extra phase existence of CIGS thin films strongly depend on the heating profile temperature and time of each step during selenization. Conventional high-temperature (515 °C) selenized CIGS thin films formed grains of approximately 2–3 µm, although the Cu–In–Ga metallic precursor was very smooth. On the other hand, the precursor selenized at a low temperature (about 400 °C) exhibited a homogeneous surface morphology because the precursor was formed from Cu–Se and (In,Ga)–Se alloys to diffuse selenide into a Cu–In–Ga metallic precursor. The high-temperature selenized CIGS thin films after low-temperature selenization had a homogeneous surface morphology with appropriate-sized grains. These results indicate that the heating profile “during” selenization was very important in forming Cu–Se and (In,Ga)–Se alloys from a Cu–In–Ga metallic precursor.

Comparison of tetraethylborate and tetraphenylborate for selenite determination in human urine by gas chromatography mass spectrometry, after headspace solid phase microextraction

Two different derivatizing reagents were tested for the development of a fast and sensitive method for the determination of selenites (Se IV) in human urine. The reagents were sodium tetraethylborate (NaBEt 4) and tetraphenylborate (NaBPh 4), respectively, and the procedure is based on in situ derivatization of selenites in aqueous medium. Selenite ions are converted to diethylselenide (DESe) or diphenylselenide (DPhSe) and subsequently collected from the headspace by solid phase microextraction using a silica fiber coated with polydimethylsiloxane (HS-SPME). Finally, they are quantitated by GC/MS in SIM mode. Ethylation over phenylation was proved preferable for the headspace extraction because of the higher volatility of the diethyl-derivative of selenites. The optimization of the HS-SPME conditions was performed both in aqueous and urinary solutions. Under the optimum conditions for HS-SPME, the gas chromatographic conditions were also optimized. Between the two alkylation reagents tetraethylborate was proved more efficient and the quantitation was satisfactory. Aqueous certified reference materials were analyzed to evaluate the accuracy of the method. The precision of the method was 4.2% and the calculated detection limit was 0.05 μg L −1 for human urine.

Sulfur versus Oxygen Reactivity of Organic Molecules at the Ge(100)-2×1 Surface

The adsorption behavior of sulfur- versus oxygen-containing organic molecules, including ethanol, ethanethiol, diethyl ether, and diethyl sulfide, at the Ge(100)-2 x 1 surface was investigated using a combination of multiple internal reflection infrared (MIR-IR) spectroscopy and density functional theory (DFT). The results show that ethanol and ethanethiol both adsorb via Ch-H dissociation at 310 K, where Ch (chalcogen) is either S or O. DFT calculations indicate that S-H dissociation is both kinetically and thermodynamically favored over O-H dissociation. IR spectra of diethyl ether and diethyl sulfide reveal that both molecules adsorb via dative bonding through the heteroatom for temperatures up to approximately 255 and 335 K, respectively, and reversibly desorb at higher temperatures. From these desorption temperatures, the S-Ge dative bond of a sulfide is calculated to be 5.9 kcal/mol stronger than the O-Ge dative bond of an ether, a trend consistent with results from DFT calculations. Moreover, for all of the molecules studied, SGe dative bonds are found to be stronger than O-Ge dative bonds, with the magnitude of the difference increasing with substitution of bulkier groups on the Ch atom of the adsorbate. Calculations on diethyl selenide show that the Se-Ge dative bond is slightly stronger than the S-Ge dative bond.

Synthesis and Charaterisation of Chromium Oxyselenide (Cr2Se0.7O2.3) Formed from Chemical Vapour Synthesis: A New Antiferromagnet

AbstractChromium oxyselenide Cr2Se0.71O2.30 was synthesised by chemical vapor synthesis of chromium oxychloride and diethyl selenide. The material adopts the Cr2Se3 structure type with a = 6.26(3) Å and c = 17.45(3) Å. The Raman spectrum shows bands at 225 and 550 cm–1. X‐ray photoelectron spectroscopy and wavelength dispersive analysis by X‐rays confirmed the material was homogeneous and of uniform composition Cr2Se0.71O2.30. The material is an antiferromagnet with a Neel temperature of 43 K. This is the first solid‐state chromium oxyselenide reported and shows that the hard oxygen and soft selenium can co‐exist in the same lattice if formed under the kinetic product conditions of a rapid gas‐phase reaction.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Atmospheric pressure chemical vapour deposition of SnSe and SnSe 2 thin films on glass

Atmospheric pressure chemical vapour deposition of tin monoselenide and tin diselenide films on glass substrate was achieved by reaction of diethyl selenide with tin tetrachloride at 350–650 °C. X-ray diffraction showed that all the films were crystalline and matched the reported pattern for SnSe and/or SnSe 2. Wavelength dispersive analysis by X-rays show a variable Sn:Se ratio from 1:1 to 1:2 depending on conditions. The deposition temperature, flow rates and position on the substrate determined whether mixed SnSe–SnSe 2, pure SnSe or pure SnSe 2 thin films could be obtained. SnSe films were obtained at 650 °C with a SnCl 4 to Et 2Se ratio greater than 10. The SnSe films were silver–black in appearance and adhesive. SnSe 2 films were obtained at 600–650 °C they had a black appearance and were composed of 10 to 80 μm sized adherent crystals. Films of SnSe only 100 nm thick showed complete absorbtion at 300–1100 nm.

Atmospheric Pressure CVD of Molybdenum Diselenide Films on Glass.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Atmospheric Pressure CVD of Molybdenum Diselenide Films on Glass

Atmospheric pressure (AP)CVD of molybdenum diselenide films on glass substrates was achieved by reaction of diethyl selenide or di-tert-butylselenide with MoCl5 at 500-650 degrees C. X-ray diffraction (XRD) showed that the MoSe2 films were crystalline with a mixed 2Hb/3R polytype stacking and typical cell constants of a = 3.28, c = 6.48 angstrom (c-axis is x 2 for the 2Hb form and x 3 for the 3R form). Energy dispersive X-ray analysis (EDAX) gave a Mo/Se ratio close to 1:2 for films formed at 600-650 degrees C, those formed at lower temperatures contained some chlorine. The films were brown in appearance, were adhesive, passed the Scotch tape, test but could be scratched with a steel scalpel. Scanning electron microscopy (SEM) showed that the films were composed of needlelike agglomerates which became longer and thinner with increasing deposition temperature. The films showed high absorbance in the visible spectrum but were more transparent in the near-infrared.

Influence of the stacking order on structural features of the Cu‐In‐Ga‐Se precursors for formation of Cu(In,Ga)Se 2 thin films prepared by thermal reaction of InSe/Cu/GaSe alloys to elemental Se vapor and diethylselenide gas

A novel partway for the fabrication of copper-indium (gallium) diselenide has been developed. This two-stage process consists of the formation of Cu-In-(Ga)-Se precursors and subsequent selenization to form CuIn(Ga)Se2. In this work, we have investigated and compared the possible interactions in Cu-In-Ga-Se systems, using sequentially stacked precursors premixed with Se, in order to get a better understanding of the Cu(In,Ga)Se2 thin film formation. Comparison of these SEM micrographs clearly revealed that the surface morphologies and hence surface roughness of the resulting Cu(In,Ga)Se2 absorber films were significantly influenced by the structure of the precursor films prior to selenization. XRD analyses revealed the presence of a graded CuIn1-xGaxSe structure, irrespective of the stacking order during the precursor formation step for samples selenized using elemental Se vapor. It was established that distinct from the case of using Se vapor, a single-phase Cu(In,Ga)Se2 films were obtained by diethylselenide (DESe) selenization from Cu-In-Ga metal precursors premixed Se irrespective of the stacking order during the precursor formation step. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Atmospheric pressure chemical vapor deposition of WSe2thin films on glass—highly hydrophobic sticky surfaces

Atmospheric pressure chemical vapour deposition (APCVD) of tungsten selenide films on glass substrates was achieved by reaction of diethyl selenide with WCl6 at 500–650 °C. X-Ray diffraction showed that the WSe2 films were crystalline with cell constants close to those expected—some preferred orientation was noted at higher deposition temperature. Energy-dispersive analysis by X-rays (EDAX) gave a W ∶ Se ratio close to 1 ∶ 2 for all the films formed at 550 °C. The films were matt black in appearance, were adhesive, passed the Scotch tape test but could be scratched with a steel scalpel. SEM showed that the films were composed of either plate or needle like crystals which become longer and thicker with increasing deposition temperature. The films were highly hydrophobic with contact angles for water droplets in the range of 135–145°. Furthermore these surfaces were highly adherent for water droplets—that did not roll or slide even at a tilt angle of 90°.

Composition and morphology of partially selenized CuIn 1− XGa XSe 2 thin films prepared using diethylselenide (DESe) as selenium source

CuIn 1− x Ga x Se 2 (CIGS) thin films are being prepared by selenization of Cu–In–Ga precursors using diethylselenide, (C 2H 5) 2Se, (DESe) as selenium source in place of H 2Se gas because of lower toxicity and ease of handling. Rough estimates indicate that selenization process using DESe would cost approximately same or slightly less compared to that using H 2Se. Price of DESe per mole is approximately five times that of H 2Se. However, partial pressure of DESe, which reflects source material consumption, is approximately three to four times less than that of H 2Se, due to higher decomposition rate of DESe compared to that of H 2Se. The actual DESe consumption would be four to ten times less compared to that of H 2Se. A selenization set-up using DESe as selenium source has been designed, fabricated and installed at FSEC Photovoltaic Materials Lab. Initial characterization of CIGS thin films have been carried out using electron probe microanalysis (EPMA), X-ray diffraction (XRD), scanning electron microscopy, secondary ion mass spectroscopy and Auger electron spectroscopy. EPMA showed elemental ratios of film to be near stoichiometric composition CuInSe 2 with very low gallium content mainly because of tendency of gallium to diffuse towards back contact. XRD data shows formation of high crystalline CuInSe 2 phase consistent with the EPMA data.

SPME–multicapillary GC coupled to different detection systems and applied to volatile organo-selenium speciation in yeast

In this work the versatility of solid phase microextraction (SPME) in combination with multicapillary gas chromatography (MC–GC) was evaluated using different common detectors for organo-selenium speciation. The methods compared for detection were inductively coupled plasma mass spectrometry (ICP–MS), microwave induced plasma atomic emission spectroscopy (MIP–AES) and atomic fluorescence spectroscopy (AFS). All detectors were found to be suitable, with highest sensitivity being obtained for MIP–AES detection, with detection limits of 0.57 ng ml−1 for dimethyl selenide, 0.47 ng ml−1 for diethyl selenide and 0.19 ng ml−1 for dimethyl diselenide. The method was applied to the determination of volatile alkyl selenides in selenium enriched yeast samples, which revealed that the presence of inorganic selenium gives rise to at least seven different volatile species after metabolization, with dimethyl diselenide the predominant species. Commercial pasteurized yeast, containing mainly selenomethionine for its use as a food supplement, was found to be still active and produces considerable amounts of organoselenium compounds.

Volatile organo-selenium speciation in biological matter by solid phase microextraction–moderate temperature multicapillary gas chromatography with microwave induced plasma atomic emission spectrometry detection

Microwave induced plasma atomic emission spectrometry (MIP-AES) in combination with multicapillary (MC) gas chromatography could be proven to be useful for element specific detection of volatile species. Solid phase microextraction (SPME) was used for preconcentration and sample-matrix separation. The fiber desorption unit as well as the heating control for the MC column were in-house developed and multicapillary column was operated at moderate temperatures (30–100 °C). The method was optimized for organo-selenium species (dimethylselenide (DMSe), diethylselenide (DEtSe) and dimethyldiselenide (DMDSe)), using a chemometric approach. Stationary phases for the separation column were optimized using a conventional GC and contrasted with the results obtained with the MC. Application was focussed on selenium accumulating biological matter, such as lupine, yeast, Indian mustard and garlic. These samples were grown in hydroponic solution containing inorganic selenium (Na 2SeO 3 and Na 2SeO 4). SPME sampling was carried out in fixed volume flow boxes in headspace above the living plants and in vials using treated samples. Results demonstrate inorganic selenium transformation into volatile organic species during metabolism. Separation is fast, a chromatogram can be obtained in less than 3 min and detection limits were at sub-ppb level for all investigated species. The system is independent from the use of a conventional gas chromatographic oven and can be used as a versatile alternative to highly cost intensive methods such as GC–ICP-MS.