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The effects of the initial pulse of tert-butyl iodide as a surfactant in atomic layer deposition of HfO2 using cyclopentadienyl tris(dimethylamino) hafnium, CpHf(NMe2)3, and ozone, O3, are investigated at 320, 300, and 250 °C. The formation of 2-methylpropene and hydrogen iodide from tert-butyl iodide via elimination reactions is the key idea of our effective approach for improving film conformality, film quality, and leakage current simultaneously. Our predicted growth mechanisms, supported by experimental results, suggest that different blocking probabilities by 2-methylpropene and hydrogen iodide on the top and bottom sides of the trench feature with an aspect ratio of 22.6:1 lead to 10% improvement in film conformality. In addition, ligand exchanges between the Hf precursor and hydrogen iodide lead to effective removal of large portions of carbon-containing ligands, resulting in a significant reduction in carbon residues, 76% at 320 °C and 40% at 250 °C, as evidenced by secondary ion mass spectrometry results. An increase in film density is also observed partly due to better completion of surface reactions between –I of Hf–I and O3. In terms of electrical properties, a significant improvement of 95% in leakage current is achieved due to the improvement in the film quality when tert-butyl iodide is employed. The deposited HfO2 film has superior leakage properties of 5.18 × 10−8 A/cm2 at 3 MV/cm, which is below the dynamic random access memory leakage current limit.

The photodissociation of hydrogen iodide in the A-band region was investigated between 273 and 288 nm using the photofragment imaging technique. At 17 wavelengths the I* (2P1/2)/I(2P3/2) branching ratio was measured by recording the corresponding hydrogen atomic fragment using multiphoton ionization at 243 nm. The branching ratios are in good agreement with previous measurements and confirm that four (final) states 3Π(0+), 3Π(1), 3Σ(1), and 1Π(1) are involved in the A-band absorption of HI and that those states dissociate adiabatically to form H+I* and H+I following parallel and perpendicular transitions, respectively. The deficiency of the model of three unbound states and that of the δ-approximation is substantiated.

The rotationally resolved, zero kinetic energy, pulsed‐field ionization (ZEKE‐PFI) spectrum of the HI+ X 2Π1/2, v+=0 level, obtained by double‐resonance excitation via the HI F 1Δ2, v=0 level, is reported. The rotational and Λ‐doubling constants for the HI+ X 2Π1/2, v+=0 level obtained from the experiment are close to those estimated theoretically by Mank et al. [J. Chem. Phys. 95, 1676 (1991)]. At higher pressures, the dissociative charge transfer reaction HI*+HI→HI++H+I− represents a potentially serious loss mechanism for the high Rydberg states that give rise to the ZEKE‐PFI signal. This result is of more general applicability, because it provides evidence that collisions of the Rydberg electron with neighboring molecules can play a significant role in ZEKE‐PFI experiments.

The spectroscopy of hydrogen iodide Rydberg states is investigated by resonantly enhanced multiphoton ionization (REMPI), utilizing time‐of‐flight mass spectrometry for detection. A (2+1) REMPI excitation mechanism provides access to electronic states in the region 64 641–71 352 cm−1. Two‐photon selection rules allow the observation of transitions forbidden in the HI absorption experiments. Many of the assigned Rydberg states contain underlying, unassigned structure with anomalous intensity fluctuations and apparent breaking off of branches. Additionally, we observe autoionized levels, most likely accessed by either a (3+1) or a direct four‐photon excitation. Molecular constants are calculated for all HI bands observed. Also included is the first REMPI study of iodine atoms coming from photolyzed HI precursor.

The reactions of hydrogen atoms, generated by ultraviolet photolysis of hydrogen iodide, with solid ethane and propane at 10 K are investigated using electron spin resonance (ESR) to identify the reaction products. Although the results are generally similar to those found by others for these tunneling hydrogen abstraction reactions in dilute solutions of the alkanes in xenon, there also are significant differences, most notably, evidence that only the secondary hydrogen of propane is abstracted in its tunneling reaction with an H atom. Also notable is the high degree of crystalline order in the ethane matrix, which is preserved in the ethyl radical product of the H atom–ethane reaction.

Rydberg electron transfer (RET) to jet‐cooled hydrogen iodide (HI) molecules has been studied for alkali atoms excited to ns and nd Rydberg levels (9

The ground‐state rotational spectra of the two isotopomers [(CH3)3N,HI] and [(CH3)3N,DI] of a dimer formed between trimethylamine and hydrogen iodine have been observed in the gas phase by the pulsed‐nozzle, F–T microwave technique. The spectroscopic constants B0, DJ, DJK, χ(14N) and χ(I) have been determined for both isotopomers and have the values 894.0954(2) MHz, 0.010 17(18) kHz, 5.880(10) kHz, −2.451(8) MHz, and −341.204(14) MHz, respectively for [(CH3)3N,HI]. It is concluded, by comparing the iodine nuclear quadrupole coupling constant χ(I) and the intermolecular stretching force constant kσ with those of model hydrogen‐bonded (H3P...HI) and ion‐pair (Na+...I−) analogs, that (CH3)3NH+...I− is the appropriate description for the gas‐phase dimer. An experimentally defined fractional ionic character indicates that the extent of proton transfer increases smoothly along the series [(CH3)3N,HX], where X=F, Cl, Br, and I. Simple energetic considerations are shown to be in agreement with this conclusion.

Hydrogen iodide, a Hund's case (c) molecule, serves as a benchmark compound for studying rich molecular state interactions between Rydberg and valence states as well as between Rydberg states at high energies (72,300-74,600 cm(-1)) by mass resolved resonance enhanced multiphoton ionization (REMPI). Perturbations in the spectra appearing as deformations in line-positions, line-intensities, and linewidths are found to be either due to near-degenerate or non-degenerate interactions, both homogeneous and heterogeneous in nature. Perturbation analyses allow indirect observation as well as characterization of "hidden states" to some extent. Furthermore, new observable spectral features are assigned and characterized.

The double photoionization of HI molecules has been investigated using vacuum ultraviolet synchrotron radiation in the energy range between 27 and 35 eV. The product ions have been detected by the use of time-of-flight mass spectrometry and the threshold energy for HI2+ and H+ + I+ formation has been determined. These results have been interpreted by the use of a theoretical model which has been previously applied by us to HBr2+ and HCl2+. On the basis of the reliability of such a model, an assessment of the systematic trends of the bond features along the HX2+ (X=F, Cl, Br, I) homologous series is given in this paper. In particular, the increase of the stability of these dications, in their lowest electronic states, when going towards the heavier molecules, has been rationalized considering the systematic variation of the charge transfer coupling between the H-X2+ and the H+-X+ states.

Oxygen atoms and ozone react with hydrogen iodide in dilute nitrogen and argon matrices at 8°K to produce new infrared absorptions at 3597, 1103, and 575 cm−1 which are attributed to the HOI intermediate species hypoiodous acid. The observed oxygen‐18 and deuterium isotopic frequencies and associated band assignments identified isolated H–O and O–I stretching modes which defined the H–O–I structural arrangement. Partially enriched oxygen‐18 and deuterium isotopic experiments confirmed the fact that the product contains one oxygen and one hydrogen atom per molecule. The vibrational spectrum of HOI is analogous to those of the other hypohalous acids.

For reaction A+A=B+C it is shown (after application of formalism similar to that used by Prigogine and Xhrouet for analysis of generalized Boltzmann equation) that the ratio k/k0 (where k and k0 are the values of rate constant in dense and dilute gas, respectively) is equal to the radial distribution function χ taken at the point of contact of reacting spheres. Comparison of theoretical results derived in this paper and experimental results due to Kistiakowsky on decomposition of hydrogen iodide is given and good agreement between those results is obtained.

Photofragment spectroscopy has been applied to the photolysis of hydrogen iodide and deuterium iodide at 37 550 cm−1 (266.2 nm). The extent of excited I(2P1/2) atom production and the symmetry of the excited molecular states leading to dissociation are derived by measuring the translational energy and angular distributions of the recoiling H and D atoms. It is found that for HI, 36%±5% of the I atoms are formed in their excited state, while for DI the fraction is 26%±3%. In both cases, the transition leading to excited atoms is parallel, agreeing with Mulliken’s spectral interpretation. These results, together with measurements reported by others at different wavelengths, are used to analyze the first absorption continuum of HI and DI. This continuum is found to be consistent with overlapping transitions to 3Π1, 3Π0+, and 1Π excited states, as predicted by Mulliken. A nonlinear curve fitting technique is applied to the available data to separate each state’s contribution to the total continuum absorption ...

The approximate study of the restricted rotation of molecules near a surface is extended to an unsymmetrical diatomic molecule, hydrogen iodide, and a ring molecule, benzene, for a graphite surface in each case. Calculations of the factor R in the BET constant C=R exp(e1—Λ)/kT are carried out for these cases. R is found to be of the same order of magnitude (2–20) as for the symmetrical diatomic molecule.

The thermal exchange of iodine with CH3I and with HI has been studied in the gas phase between 60° and 140°C. The exchange is strongly surface sensitive and follows the rate law: R=k1(CH3I)(I2)+k2(CH3I). The exchange proceeds by means of two competing mechanisms, one of which is independent of iodine concentration and possibly involves the formation of CH3· free radicals on the surface which then react with I2. This heterogeneous reaction may be eliminated by preheating the reaction vessel overnight at 550°C, which reduces the reaction to a simple bimolecular exchange following the rate law: R=(CH3I)(I2)(2.5×106)exp(−9000/RT) moles−cm−3−sec−1 which was obtained specifically for a surface/volume ratio of 1.19 cm—1.The formation of a complex between CH3I and I2 was studied spectrophotometrically in dry n‐heptane. The heat of formation of the complex was found to be —4.5 kcal mole—1, and the entropy of formation was found to be —25.8 cal deg—1 mole—1 for a standard state of 1 mole‐liter—1. The formation of a...

The photodissociation of hydrogen iodide by light of λ2537A has been utilized as a source of hydrogen atoms for a study of their subsequent reactions with iodine and the hydrogen halides. The observed rate of hydrogen formation has been used to evaluate the ratio of rate constants for the following reactions: H+HX→H2+XH+I2→HI+I where X represents Cl, Br or I.

The reactions of hot hydrogen atoms in the range 0.8–2.4 eV with perdeuterated and partially protonated hydrocarbons have been studied. The hot atoms were produced in C2D6, C3D8, n‐C4D10, and various isotopically mixed ethanes by flash photolyzing HI‐RHD mixtures. Graphs of product ratio H2/HD vs the initial reactant ratio HI/RD were characteristically linear. These and similar graphs for mixtures containing a rare gas were analyzed using the kinetic theory of hot‐atom reactions developed by Estrup and Wolfgang and also by a simpler approach. Where comparison was possible, the results of the two methods of analysis showed good agreement. The following parameters were evaluated: average relative reaction probabilities for H*–HI and H*–RD collisions (where the asterisk denotes the hot species), the fraction of H* moderated to that reacting hot in pure RD, and β, the average fractional energy loss by H* is collision with RD. The most important conclusions which can be drawn from the results are: (a) a simple...

The results of experiments to determine reaction cross sections for the formation of HD in energetic collisions of HI with DI are reported. Molecular beams of HI, accelerated to energies of 40–215 kcal/mole by expansion from nozzles in mixtures with hydrogen or helium, were passed through a reaction chamber containing DI at low density. A mass‐spectrometer monitoring the gases effusing from the chamber was used to detect the HD reaction product. In the range of collision energies investigated, at approximately one‐half to two and one‐half times the activation energy of 44 kcal/mole, no HD attributable to reaction was detected. With HD formation assumed to be that corresponding to the lower limit of detection, the upper limit to reaction cross section is determined to be 0.04 A2. Comparison is made with several models for reaction with differing energy requirements. The results indicate that rotational or vibrational excitation of colliding partners is required for an appreciable probability of reaction upon collision.

The rate of photochemical production of hydrogen iodide in a hydrogen—iodine system irradiated with 5780‐A light was measured and found to be proportional to the square of the iodine atom concentration. Absolute light intensities were determined and rate constants were calculated for the termolecular reaction H2+2I→2HI at 417.9°, 480.7°, 520.1°K. The previously obtained thermal data in the range 633°—738°K were treated considering one of the elementary reactions to be the termolecular reaction and not H2+I2→2HI; the rate constants obtained have the same Arrhenius parameters as those from the photochemical measurements. The bimolecular reaction, H2+I2→2HI, does not occur. Two mechanisms consistent with the photochemical and the thermal data are H2+2I→2HI; H2+I+M=H2I+M, H2I+I→2HI. The specific rate calculated for the termolecular reaction is k=(6.66±0.5)×107 exp (−5310±85/RT) liter2 mole−2·sec−1.

The relative rates of the reactions of hydrogen iodide and deuterium iodide with methyl iodide were studied by a competitive method at 310° and 250°C. The analysis of hydrogen‐deuterium mixtures was accomplished by means of a simple viscometer with an accuracy of 0.5 percent. It was found that hydrogen iodide reacts about 1.4 times as fast as deuterium iodide at both temperatures. These results are discussed in terms of Eyring's theory of absolute reaction rates and a simple model.

Methyl iodide, hydrogen iodide, and deuterium iodide have been irradiated with x rays, whose energies are such that the most probable event is the formation of a vacancy in the L shell of iodine. The readjustment to this vacancy, principally by a series of Auger processes, gives rise to extensive ionization and decomposition; and the relative abundances of the fragment ions and their recoil‐energy spectra have been measured with a specially designed mass spectrometer. As the result of the inner‐shell vacancy, CH3I decomposed primarily into hydrogen, carbon, and iodine ions, having, respectively, the average charges of 1+, 2+, and 5+. Very few molecular ions were observed. The recoil energies were quite large with values in some cases above 100 eV. A calculation, based on a simple model for a Coulombic ``explosion,'' is shown to be consistent with the data. In the studies made with HI and DI the recoil spectra of H+ and D+ are compared with calculations of the kinetic energies expected from multiple ionization. From this comparison there appears to be evidence that the multiply charged molecular ions separate slightly during the time the Auger processes are taking place. Finally, a brief discussion is given concerning the importance of the initial consequence of x‐ray interaction in radiation damage.

The flash photolysis of hydrogen iodide in the presence of nitrous oxide, carbon dioxide, and water has been investigated by kinetic spectroscopy. Although the fraction of hydrogen iodide dissociated was very large, the only observable intermediate was imidogen. It was demonstrated that the rapid removal of imidogen and the apparent absence of hydroxyl radicals in each case is a result of the following two reactions, respectively: (1) NH + HI yields NH2 + I; and (2) OH + HI yields H2O + I.

Measurements on 13 lines in the hydrogen iodide fundamental vibration—rotation band have yielded a set of line strengths of considerable accuracy. From these strengths a total band intensity of 0.37 cm—2 atm—1 at 300°K has been computed, as well as a value for the vibration—rotation interaction parameter θ which is found to be —5. Both of these figures indicate that the ``effective charge'' of this molecule is remarkably small, which fact is reflected in a great dominance of the R branch over the P branch. Using the line strengths as input data, linewidths have been computed from equivalent width measurements. Finally, the linewidths have been converted to optical collision cross sections. The J dependence of the linewidths and the collision cross sections is not typified by the other hydrogen halides. The usual resonance peak is absent and a lower limiting value seems to be reached by | m |=3. Furthermore, the collision cross sections for the lines of higher J are much larger than might be inferred from the other hydrogen halides.

The abnormal upfield bias of the proton chemical shift in hydrogen halides, HX, on going from X = F to I is examined theoretically in terms of the third‐order perturbation theory including the spin‐orbit interaction (λL · S). The expression for the new type of shielding constant σLS is presented in its complete form and in simplified form with the average excitation energy approximation. The numerical calculations using semiempirical SCF wavefunctions predict substantial contribution (51%) of this shielding effect (σLS) to the total shielding of the proton in hydrogen iodide.

Acetone over a range of pressures and temperatures (1.2–15 cm Hg; 126–295°C) was photolyzed with light of 3130 A in the presence of small amounts of hydrogen iodide. The primary process was found to be the C–C split to form acetyl and methyl radicals. Hydrogen iodide acted as an excellent radical ``trap'' for these radicals. No spontaneous decomposition of acetyl radicals was observed. Relative rates of methyl radical reactions with iodine and hydrogen iodide were measured. Complications due to surface effects in these reactions are considered.Kinetic constants for the reactions CH3+HI→CH4+I(1); CH3+I2→CH3I+I(2) are E1—E2=1.3±0.5 kcal, A2/A1=2.4, and log(k1/k2) = —0.38–1300/4.575T.Above 200°C the acetyl radical decomposition is measurable and the rate constant is observed to be pressure dependent. The pressure dependence is treated by an approximate method related to the Hinshelwood‐Lindemann equation and the high‐ and low‐pressure limiting rate constants are given by logk∞=10.3–15 000/4.575T sec—1, logk0...

Rosenbaum and Hogness [E. J. Rosenbaum and T. R. Hogness, J. Chem. Phys. 2, 267 (1934)] measured the rate of para to ortho hydrogen conversion in equilibrium mixtures of hydrogen, iodine, and hydrogen iodide and found that the conversion rates were about twice as fast as would be predicted by the reactions H2+I2↔ lim (2)(1)2HI. In this paper the additional conversion in their experiments is shown to be explained by the reaction sequence (3)I+H2→HI+H(4)H+HI→H2+I(5)H+I2→HI+I(6)I+HI→I2+H. The rate constants for the rate determining steps (1) and (3) as determined from the equilibrium data are shown to be equal to those determined in systems far from equilibrium. Upper limits can be set on the rates of two para to ortho hydrogen conversion reactions which have previously been suggested to explain the results of Rosenbaum and Hogness: an upper limit of 2.5×10—12 is determined for the collision efficiency of reaction (a) and a lower limit of 47 kcal is determined for the activation energy of (b) (a)H2p+I→H2o+I(b)H2p+HI→H2o+HI. The reactions of hydrogen, both with iodine atoms and with iodine molecules, are shown to be homogeneous in Pyrex vessels at 693°K.

A theory of phase changes due to hindered molecular rotation in crystals is developed on the basis of classical statistical mechanics. It is demonstrated that local hindrance of relative rotation of neighboring molecules in the lattice can produce a non‐uniform distribution in orientation below a certain critical temperature. The theory provides a semi‐quantitative description of the behavior of the hydrogen halides in certain of their lambda‐transitions, with a relative torque potential of the form (e/2) cos γ for a pair of neighboring molecules, the axes of which are inclined at an angle γ to each other. The barrier height e is estimated to be between 200 and 300 cal./mole for hydrogen iodide and hydrogen bromide.

The rate of conversion of para to ortho hydrogen was determined in the presence of equilibrium concentrations of hydrogen iodide and iodine. From these data, velocity constants and collision efficiencies for the conversion by iodine atoms were calculated. The results are in agreement with a theoretical equation derived by Wigner.

The kinetic data of Rollefson and Faull for the iodine‐catalyzed decomposition of acetaldehyde are summarized, and the RF mechanism of the reaction is critically reviewed. A new mechanism for the iodine‐catalysis reaction is presented. Properties predicted from the new mechanism are compared with the observed reaction rates, reaction orders, and the unusual experimental behavior of the reactive system. Excellent agreement is found. The reaction is initiated by an iodine atom attack on acetaldehyde to abstract a hydrogen atom and produce hydrogen iodide and an acetyl radical. The rate‐determining step for the reaction is the decomposition of the acetyl radical, which is a unimolecular pressure‐dependent decomposition. The characteristic falloff of the rate of decomposition in the later stages of reaction is shown to be the result of this pressure dependence. The mechanism is also applied to the iodine‐catalyzed decomposition of propionaldehyde. Satisfactory agreement with observed reaction orders and reaction rates is obtained. From these data the decomposition kinetics of the propionyl radical is predicted to be pressure‐dependent at normal experimental pressures.

Partition functions have been calculated for HI, I2 and I atom between 298.1 and 1500°K from spectroscopic data and the results have been fitted to a free energy equation of the usual thermodynamic form which may be differentiated and integrated to give change of heat content, specific heat and entropy for chemical reactions involving HI, I2, I and H2. The experimentally determined equilibrium constants for the reactions I2→2I and HI→½H2 +½I2 have been compared with the theoretical equilibrium constants. For the latter reaction, it is shown that the results of Bodenstein may be in error due to incorrect temperatures. Reliable values have been given for the heat of dissociation of iodine and hydrogen iodide at 25°C.

A classical trajectory analysis for the reaction H+I2→ HI+I at 600°K, using trajectories sampled within the transition region, shows vibrational excitation of the HI product molecules, mainly to the v=3 to v=5 levels. The calculated thermal rate is in approximate agreement with measurements by Sullivan. The product angular distribution is peaked at 110–120° relative to the incident atoms as measured for the reaction of D atoms by McDonald, LeBreton, and Herschbach. The translational energy distribution of the products is also similar to that found by McDonald et al. for the deuterium analog.