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The review is devoted to the capabilities of gas chromatography–mass spectrometry in the analysis of high-purity volatile hydrides of naturally occurring and isotopically enriched compositions. Problems related to experimental techniques, chromatographic separation, identification, and quantitative determination of impurities are discussed. The application of this method has significantly expanded data coverage on the nature, number, and limiting possibilities of the determination of impurities in volatile inorganic hydrides. The identified impurities are compounds of various classes. Among them are atmospheric gases; saturated, unsaturated, and aromatic C1–C9 hydrocarbons; chlorine- and fluorine-containing C1–C4 hydrocarbons; homologues and alkyl derivatives of hydrides; Si2–Si4 siloxanes; fluorosiloxanes; oxygen-containing hydrocarbons; sulfur-containing substances; and hydrides of other elements. Gas chromatography–mass spectrometry analysis made it possible to detect the presence of impurities in isotopically enriched silicon and germanium hydrides, which are their molecular isobars. The use of gas chromatography–mass spectrometry in the analysis of high-purity inorganic hydrides makes it possible to reach the detection limits of impurities of 10–8–10–5 mol %.

We present our findings on the use of diode laser spectroscopy (DLS) for monitoring СО2, Н2О, СН4, C2H2, C2H4, NH3, and other gas impurities during low-temperature fractional distillation purification of gaseous hydrides. We demonstrate a lineup of instruments and techniques for continuously monitoring impurities during purification of hydrides: NH3, AsH3, РН3, and SiH4. The IR sources used are distributed feedback diode lasers (DLs) having a single mode output fiber pigtail and covering the near-IR spectral region, from 0.7 to 2.0 μm, where overtone and combination absorption bands of the impurities of interest are located. The systems offer high sensitivity and speed in impurity concentration measurements. Owing to their small size and low energy consumption, they can readily be integrated into a process equipment (components of fractionation columns) and enable prolonged continuous monitoring of the purity of hydrides. We describe gas concentration measurement techniques that use conventional high-resolution differential absorption spectroscopy and new, modulation correlation approaches for monitoring a weak molecular absorption by an impurity of interest against a strong selective absorption background of a matrix substance (hydride under study). We present results of technological experiments concerned with the low-temperature fractional distillation of hydrides and the degree of impurity removal from them as monitored by DLS.

The impurity composition of natural and isotopically enriched silane obtained from magnesium silicide and silicon tetrafluoride is studied by gas chromatography–mass-spectrometry. The impurities characteristic of silane with natural and isotopically enriched composition are atmospheric gases; carbon dioxide; hydrides; saturated, unsaturated, and aromatic hydrocarbons; halogenated hydrocarbons; alkyl derivatives and silane homologues, siloxanes. The impurity content of high-purity silane does not exceed 10–7–10–5 mol % After synthesis, the concentrations of impurities in the silane and fractions isolated by its distillation purification lie in the range n × 10–6 − n × 10 mol % The limits of detection for impurities are 1 × 10–8–9 × 10–4 mol %

A method of chromatography–mass spectrometry is used to study the impurity composition of arsine synthesized by the reaction of arsenic chloride with sodium borohydride. Capillary adsorption columns with adsorbents modified silica and polytrimethylsilylpropine is used for the separation of impurities. Impurities are identified by comparing their mass spectra with the NIST database, published data, as well as by reconstructing their structures from fragment ions. Impurities of permanent gases; saturated and unsaturated hydrocarbons C1–C6; chlorinated, oxygenated, and aromatic hydrocarbons; volatile inorganic hydrides; and alkyl derivatives of arsine, trimethyl fluorosilane, carbon sulfur dioxide, and dimethyl sulfide are identified in arsine. Mass spectra of C2H3AsH2, CH3AsHC2H5, and C2H5As2H3 impurities are obtained for the first time.

The method of chromatography–mass spectrometry is used to study the impurity composition in monosilane obtained in the reaction of magnesium silicide with ammonium chloride in liquid ammonia. To improve the reliability of the impurity identification, along with the study of pure monosilane samples, we analyzed monosilane fractions isolated upon purification by low temperature rectification. To separate the impurities of permanent gases, hydrocarbons C1–C3, volatile inorganic hydrides, disilane, and alkylsilanes, we used an adsorption capillary column GS-GasPro 60 m × 0.32 mm with a modified silica gel. To separate the homologs of monosilane, siloxanes, and alkylsilanes, we used a column 25 m × 0.26 mm, df = 0.25 μm with a polytrimethylsilylpropyne (PTMSP) sorbent. The impurities were identified by comparison of their experimental mass spectra with the NIST database. In the absence of the mass spectra of analytes in the NIST electronic database or in the case of their low coincidence with the database spectra, the identification was performed using mass spectra and retention times published in the literature. The impurities of permanent gases, carbon dioxide, hydrocarbons C1–C3, volatile inorganic hydrides, monosilane homologies, siloxanes, and alkyl silanes were identified in monosilane. Quantitative determination of the impurities was carried out in the mode of selective ion detection using the mass numbers for which the signal-to-noise ratio was maximal. Their concentrations were calculated using a method of absolute calibration by the peak areas; in the case where reference samples were absent, the concentrations were determined using the dependence of the sensitivity coefficients of their detection on the magnitude of the total ionization cross sections. The detection limits of the impurities range within 1 × 10–5–2 × 10–7 mol %. The accuracy of the analysis was verified by the method of sample size variation. The results of determination of the impurities in monosilane after synthesis, as well as in monosilane purified by low temperature rectification and in the isolated fractions with concentrated higher and lower boiling impurities, are reported.

Chromatography-mass-spectrometry was used to examine the stability of admixtures of C1−C7 hydrocarbons, fluorine and chlorinated derivatives of hydrocarbons, alkyl derivatives of silane, homologs of monosilane, and siloxanes in monosilane in its storage in molybdenum-glass ampules and stainless-steel cylinders. It was found that, in the case of storage in glass ampules, the concentration of ethylene and tetrafluoroethylene admixtures decreases and that of ethyl silane and disilane increases. When monosilane is stored in a stainless steel cylinder, the concentration of the acetylene admixture it contains changes.

The procedure of gas chromatography/mass spectrometry determination in arsine of high purity was described for impurities of permanent gases, carbon dioxide, C1–C5 hydrocarbons, and hydrides of groups 4–6 of Mendeleev’s periodic table of elements. The detection limits of impurities took values from 2 × 10−5 to 2 × 10−7 mol %.

Using high-resolution IR spectroscopy, we have compared the impurity compositions of monosilane (SiH4) fractions enriched in impurities in the process of cryofiltration and low-temperature distillation of monosilanes derived from silicon tetrafluoride (SiF4) and trichlorosilane (SiCl3H). The results demonstrate that the more volatile impurities present in both monosilanes are methane (CH4) and carbon dioxide (CO2), whereas the impurities specific to the fluoride-derived monosilane are SiF4, SiF3H, and SiF2H2. The less volatile impurities common to both monosilanes are ethane (C2H6), disiloxane (Si2H6O), and disilane (Si2H6); the impurities specific to the fluoride-derived monosilane are tetrafluoroethylene (C2F4) and monofluorosilane (SiFH3); and those specific to the chloride-derived monosilane are hydrogen chloride (HCl) and the chlorosilanes SiClH3, SiCl2H2, and SiCl3H.

Using the TDLS method it has been found that ammonia (NH3) is the main impurity in arsine (AsH3) and phosphine (PH3), produced by hydrolysis of magnesium arsinide and phosphinide, respectively. NH3 behavior is abnormal in solutions of these hydrides: NH3 reveals the properties of a more volatile impurity in relation to arsine and phosphine, although its boiling temperature is higher than that of AsH3 and PH3. The observable anomaly is connected with the fact that in solutions of arsine and phosphine NH3 shows properties differing from the properties of pure ammonia. It was supposed that the influence of intermolecular interaction between ammonia molecules, when diluted by arsine or phosphine, decreases. During the purification of arsine or phosphine one must continuously monitor the NH3.concentration in the extraction of the light fraction in order to define the point at which to terminate the purification process.

The technique of growing CdTe and Cdx Hg1 − x Te layers utilizing chemical metalloorganic compound vapor deposition (MOCVD) onto a CdZnTe(111) substrate with a preliminarily deposited Cd y Hg1 − y Te layer using liquid phase epitaxy (LPE) has been developed. No noticeable changes in the electrophysical parameters and composition of the Cd y Hg1 − y Te layer take place under such conditions during MOCVD deposition.

We have developed analytical techniques for the determination of impurities in isotopically enriched 28SiH4 and 28SiF4. The impurities in SiF4 were first determined by IR spectroscopy, and those in SiH4, by gas chromatography/mass spectrometry. High-sensitivity determination of organic impurities in SiH4 and SiF4 was performed by gas chromatography. SiF4 was found to contain C1–C4 hydrocarbons, hexafluorodisiloxane (Si2F6O), hydrogen fluoride, trifluorosilanol (SiF3OH), fluorosilanes, water, and carbon oxides. The impurities identified in SiH4 include C1–C4 hydrocarbons, disilane (Si2H6), inorganic hydrides, Si2H6O, alkylsilanes, and fluorinated and chlorinated organics. The detection limits of IR spectroscopy were 3 × 10−3 to 5 × 10−5 mol %, those of gas chromatography/mass spectrometry were 8 × 10−6 to 10−8 mol %, and those of gas chromatography were 6 × 10-6 to 2 × 10−7 mol %.

Metalorganic chemical vapor deposition from Cd and Te alkyl compounds and Hg vapor is used to grow p-type Cd x Hg1 – x Te epitaxial layers on semi-insulating GaAs(111)Bsubstrates by the interdiffused multilayer process (alternating CdTe and HgTe layers) at a substrate temperature of 350°C, followed by postgrowth annealing. Layers are obtained with x = 0.2–0.4, 77-K carrier concentrations in the range (1–5) × 1016 cm–3, and 77-K carrier mobilities from 200 to 400 cm2 /(V s). The rocking curves of the epilayers have a full width at half maximum in the range 2–4 min of arc.

ZnTe and Cd1 – y Zn y Te epilayers were grown on GaAs(111)B and GaAs(100) substrates by metalorganic chemical vapor deposition. The structural perfection and surface morphology of the layers were investigated by double-crystal x-ray diffraction and scanning electron microscopy. The effect of deposition conditions on the growth rate, zinc content (y), surface morphology, and structural perfection of the epilayers was studied. The results suggest that the optimal structures for depositing HgCdTe(111)B and HgCdTe(100) are CdTe(111)B/GaAs(111)B and CdTe(100)/ZnTe(100)/GaAs(100), respectively.