Experimental and Theoretical Study of the Formation of Germanium−Carbon Ion Species in Gaseous Germane/Ethene Mixtures

Abstract

The gas-phase chemistry of gaseous germane/ethene mixtures has been investigated by ab initio theoretical calculations and by experiments to examine the formation and growth of germanium-/carbon-containing species. Ion/molecule reactions in GeH 4 /C 2 H 4 mixtures have been studied with an ion trap mass spectrometer. Ion abundance variations as a function of reaction time, reaction paths originating from primary ions of both reagents, and reaction rate constants of the main processes have been determined. The highest yield of new Ge-C bonds formed via reactions of Ge-containing ions with ethene molecules was obtained in mixtures carrying similar amounts of germane and ethene. Reactions of GeH 2 •+ with ethene play a prominent role in this system. High-level theoretical methods were therefore used to determine the geometrical structures and energies of transition structures, reaction intermediates, and final products for several reaction pathways. Formation of the adduct between GeH 2 •+ and H 2 CdCH 2 is the initial step. This process is fairly exothermic, and the free energy of the system allows several transformations. Isomerization pathways and H, H 2 , or CH 3 • loss pathways starting from this adduct have been explored. The free energy threshold defined by the first step shows that some transformations are likely to occur, whereas others can be regarded as inaccessible. Last, two theoretical methods have been used to compute the heats of formation of the attainable GeC 2 H n + species.

Gas‐phase ion chemistry in germane–propane and germane–propene mixtures

“…The present results are in good agreement with those published in a previous paper for the germane–ethene system 25. In fact, in both mixtures the C n H m + ions react with germane mainly by charge transfer or hydride abstraction reactions, thus not leading to Ge‐C species.…”

“…These latter experimental values are compared with collisional rate constants in order to obtain reaction efficiencies. The present results are compared with those obtained from the study of silane–propane and silane–propene mixtures24 and with those concerning the germane–ethene system,25 studied previously.…”

“…All experiments were run on a Finnigan ITMS mass spectrometer maintained at 333 K, in order to obtain results comparable to those from studies of other systems 24, 25. The theory and operating methods of ion trap mass spectrometry were described in previous papers 22, 26, 27.…”

Negative ion clusters in self‐condensation of GeH4

“…Gas‐phase chemistry has given remarkable contributions to elucidate the intrinsic reactivity of ions in the absence of perturbing effects due to solvents or counterions 1,. 2 Systems containing volatile compounds of silicon3,, 4 or germanium5–7 and their mixtures with small hydrocarbons8–10 have been studied by ion trap mass spectrometry and Fourier transform mass spectrometry. Fundamental aspects, such as the mechanisms of ion/molecule reactions, have been investigated and the rate constants of the first reaction steps determined and compared with the collisional rate constants calculated by the Langevin or ADO (average dipole orientation) theories 11.…”

Negative gas‐phase ion chemistry of GeH4: a quadrupole ion trap study

“…In the past years, our research group has been deeply involved in the study of the gas‐phase ion chemistry of germanium hydrides by different mass spectrometric techniques. Self‐condensation reactions10, 11 and gas‐phase mixtures of germane or methylgermane with hydrides of C and/or N, P were studied in order to obtain information on the early ion clustering reactions that eventually lead to deposition of doped germanium carbides 12–23. Recently, our attention has shifted to negative germane ions, which were observed to give extensive condensation reactions in the relatively high‐pressure environment of a triple quadrupole mass spectrometer 24.…”