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5379. An XPS study of ion-reduced dissociation on metal carbonate surfaces
Classified abstracts 5372-5380 some indication as to the disordering mechanism leading to amorphous production. (GB) R P Webb and G Carter, Rad Effects, 59, 1981, 60-76. 35 5372. The effect of germanium ion implantation dose on the amorphization and recrystallization of polycrystalline silicon films. (USA) Polycrystalline Si films have been amorphized by implantation with 130-KEY G:e ions and subsequently recrystallized by conventional heat treatment, it is found that, after amorphization with a low ion dose, recrystallization produces a structure which is morphologically similar to the original film. By contrast, after high Ge close implantation, recrystallization proceeds dendritically. An initial rationale for this behaviour is proposed in terms of the lattice disorder introduced by ion implantation. (Israel) Y Komem and I W Hall, J Appl Phys, 52 (11), 1981, 6655-6658. 35 5373. Effects of rf power and reactant gas pressure on plasma deposited amorphous hydrogenated silicon. (USA) The properties of amorphous hydrogenated silicon films produced at room temperature by rf glow discharge decomposition of silane have been studied while systematically varying the rf power and the pressure of the reactant gas. The structure and composition of the films were monitored by measuring the optical gap, IR vibrational spectrum, and the hydrogen evolution rate. Evidence is seen for an improvement of film quality at high rf power levels. Such improvement is discussed in terms of energetic ion bombardment of the growth surface. The significance of ion bombardment is emphasized by comparing films grown simultaneously on biased and unbiased electrodes. Increasing pressure moderates the ion bombardment energies and diminishes the film quality. J E Potts et al, J Appl Phys, 52 (11), 1981, 6665-6672. 35 5374. Radiation damage in silicon. (USA) Silicon specimens have been irradiated at temperatures up to 650°C, and the resultant structures examined in detail. The principal defect is an extrinsic {113} fault, elongated in <110), with a displacement close to a~11( 113 ). Below 500°C these defects may change plane, along their long axes, such that the angle between faces is obtuse. Between 500°C and 600°C isolated {113 } faults may unfault, to form interstitial loops on {113}, elongated in (110), with b=a/2(llO). At 650°C, complex unfaulting, involving two intersecting {113} faults, may occur. Nickel-implanted silicon was found to contain a variety of unfaulted and complex defects after annealing at 800°C. No evidence of interstitial aggregation to form a / 3 ( l l l ) faults on {111} was found, and it is suggested that {111} precipitates require the presence of oxygen. The tetrahedral model for the {113} fault is developed, and it is shown that this may account for all defects found in irradiational silicon and germanium, and in implanted silicon after annealing in an inert (i.e. oxygen-free) environment. (GB) I G Salisbury and M H Lorette, Rad Effects, 59, 1981, 59-68. 35 5375. Radiation damage and recovery effects in p-type lnSb. (USA) P-type InSb (nh=7.5xl019 m -a) has been irradiated with 1-MeV electrons at 7 K followed by isochronal annealing between 80 and 346 K. Changes in carrier mobility and concentration have been monitored. Effects of compensation are elucidated as is the role of shallow defect levels. (Australia) S Myhra, Rad Effects, 59, 1981, 1-6. 35 5376. Effect of forming gas anneal o n AI-SiO 2 internal photoemission characteristics. (USA) Internal photoemission characteristics from the AI-SiO 2 interface are markedly affected by a 400°C 20 rain forming gas (90% N 2 and 10% H2) anneal. The barrier height is raised by about 0.25 eV and the electric field dependence of the photocurrent is increased. P M Solomon and D J DiMaria, J Appl Phys, 52 (9), 1981, 5867-5869. 35 5377. Displacement criterion for amorphization of silicon during ion implantation. (USA) Results of Boltzmann transport equation calculations are used to estimate what fraction of a crystalline silicon lattice must be displaced to cause a crystalline-to-amorphous transition during ion implantation. Comparison of these calculations with experimental MeV He channelling and backscattering results for 150-keV boron implantation at 77°K indicates that the displacement of about 10% of tl~e lattice will cause amorphization provided the substrate is at a temperature which inhibits self-annealing processes and defect diffusion. The calculations also
indicate that the number of atoms displaced is proportional to the deposited energy density, one displacement occurring on average for each 200 eV of deposited energy. Experimental results for room-temperature silicon implantation confirm the fact that higher temperature substrates require a greater fractional displacement of the lattice before amorphization occurs. L A Christel et al, J Appl Phys, 52 (12), 1981, 7143-7146. 35 5378. Characteristics of submicron pores obtained by chemical etching of nuclear tracks in polyearbonate films. (USA) Calibrated pores in the range 102-2 X 103 A have been obtained by chemical etching of polyearbonate thin films irradiated with high energy krypton ions (500 MeV, Kr 2s + ). Both the amorphous and the crystalline forms of polycarbonate (Makrofol, Bayer), further designated by their respective trade names N and KG, have been investigated up to thicknesses of 60/an, close to the theoretical ion range of 77/~m, From conductivity studies, three different domains have been separated around the ion track: A highly damaged core of radius -~ 50 A with a fast etching rate Vr~ 104 A/min, an intermediate zone of radius =500 A with an etching rate or-0.9 A/min, an outer region with an etching rate equal to that of the undamaged material, v~=0.47 A/min. These observations are compatible with the delta ray model for track formation in plastic materials. Scanning electron microscope investigations have revealed that the pores formed in the N material are straight cylinders with a narror distribution of the pore entrance diameters. On the other hand, the pores for the KG type are much less uniform and appear to be tapered, the difference between the two sides of the membrane being as much as 50%. These characteristics could be related to inhomogeneities in the morphological structure due to (i) the finite size of the crystalline domains and (ii) an asymmetric manufacturer's processing of the film surfaces. (France) G Guillot and F Rondelez, J Appl Phys, 52 (12), 1981, 7155-7164. 35 5379. An XPS study of ion-reduced dissociation on metal carbomte surfaces. (GB) Ion-induced chemical decomposition during ion bombardment of surfaces is well known but the causes and mechanisms of this damage are still poorly understood. In general, it has been found that molecules with low free energies of formation will undergo ion-induced dissociation, but attempted correlation with thermochemical data has met with only limited success. Most experimental studies of ion-beam damage have been carried out on metal oxide substrates, which often undergo decomposition or reduction via a number of intermediate species, and result in the formation of a variety of complex reaction products. For this reason. thermodynamic models of the sputtering process have tended to be oversimplified. Better correlation with experiment would be expected within a selected range of chemically similar compounds, which undergo ion-induced decomposition via simple, one-step, irreversible reaction mechanisms to yield unique products. One such class of compounds is the alkaline earth carbonates, which undergo thermal dissociation in the solid state: MCO3(s)-,MO(s)+CO2(g) A G = 15.6 to 51.6 kcal mol-1 where M = Mg, Ca, St, Ba. Photoelectron spectra from clean alkaline earth carbonate surfaces show a single, discrete, oxygen 1 s feature, at a binding energy of about 531 eV, and an oxygen to carbonate-type carbon atom ratio of 3:1. Following exposure to the ion beam, however, both the carbon 1 s and the 53 ! eV oxygen I s peaks are observed to be significantly reduced in intensity, and a second oxygen 1 s feature, at a binding energy of about 528 eV, is produced. This new feature may be assigned to the oxide dissociation product, since further ion etching simply results in a further loss of intensity from the carbonate features, and a complementary increase in intensity from the new oxygen feature. The extent of decomposition at any given ion dose may be related to the thermochemical properties of the parent carbonate. Implications of the work in the interpretation of sputter-depth profiles of such systems are discussed. A B Christie et al, Vacuum, 31 (10-12), 1981, 513-517. 35 5380. The oxygen effect in the growth kinetics of platinum silicides. (USA) Silicide formation is strongly affected by the presence of oxygen contained in the metal film. A study has been performed by heating at various times and temperatures samples constituted by a thin Pt film sputter deposited on a silicon substrate. Four different oxygen concentrations were implanted in the Pt film ranging from 1 to 0.1 atm?/o. The presence of oxygen slows down the growth rate of Pt2Si. At 315°C in the sample with an oxygen concentration of I atm%, about 1000 A of Pt2Si are formed after 20 min of annealing. During the silicide formation, the oxygen originally contained in the platinum films segregates at the Pt28i/Pt 771
indicate that the number of atoms displaced is proportional to the deposited energy density, one displacement occurring on average for each 200 eV of deposited energy. Experimental results for room-temperature silicon implantation confirm the fact that higher temperature substrates require a greater fractional displacement of the lattice before amorphization occurs. L A Christel et al, J Appl Phys, 52 (12), 1981, 7143-7146. 35 5378. Characteristics of submicron pores obtained by chemical etching of nuclear tracks in polyearbonate films. (USA) Calibrated pores in the range 102-2 X 103 A have been obtained by chemical etching of polyearbonate thin films irradiated with high energy krypton ions (500 MeV, Kr 2s + ). Both the amorphous and the crystalline forms of polycarbonate (Makrofol, Bayer), further designated by their respective trade names N and KG, have been investigated up to thicknesses of 60/an, close to the theoretical ion range of 77/~m, From conductivity studies, three different domains have been separated around the ion track: A highly damaged core of radius -~ 50 A with a fast etching rate Vr~ 104 A/min, an intermediate zone of radius =500 A with an etching rate or-0.9 A/min, an outer region with an etching rate equal to that of the undamaged material, v~=0.47 A/min. These observations are compatible with the delta ray model for track formation in plastic materials. Scanning electron microscope investigations have revealed that the pores formed in the N material are straight cylinders with a narror distribution of the pore entrance diameters. On the other hand, the pores for the KG type are much less uniform and appear to be tapered, the difference between the two sides of the membrane being as much as 50%. These characteristics could be related to inhomogeneities in the morphological structure due to (i) the finite size of the crystalline domains and (ii) an asymmetric manufacturer's processing of the film surfaces. (France) G Guillot and F Rondelez, J Appl Phys, 52 (12), 1981, 7155-7164. 35 5379. An XPS study of ion-reduced dissociation on metal carbomte surfaces. (GB) Ion-induced chemical decomposition during ion bombardment of surfaces is well known but the causes and mechanisms of this damage are still poorly understood. In general, it has been found that molecules with low free energies of formation will undergo ion-induced dissociation, but attempted correlation with thermochemical data has met with only limited success. Most experimental studies of ion-beam damage have been carried out on metal oxide substrates, which often undergo decomposition or reduction via a number of intermediate species, and result in the formation of a variety of complex reaction products. For this reason. thermodynamic models of the sputtering process have tended to be oversimplified. Better correlation with experiment would be expected within a selected range of chemically similar compounds, which undergo ion-induced decomposition via simple, one-step, irreversible reaction mechanisms to yield unique products. One such class of compounds is the alkaline earth carbonates, which undergo thermal dissociation in the solid state: MCO3(s)-,MO(s)+CO2(g) A G = 15.6 to 51.6 kcal mol-1 where M = Mg, Ca, St, Ba. Photoelectron spectra from clean alkaline earth carbonate surfaces show a single, discrete, oxygen 1 s feature, at a binding energy of about 531 eV, and an oxygen to carbonate-type carbon atom ratio of 3:1. Following exposure to the ion beam, however, both the carbon 1 s and the 53 ! eV oxygen I s peaks are observed to be significantly reduced in intensity, and a second oxygen 1 s feature, at a binding energy of about 528 eV, is produced. This new feature may be assigned to the oxide dissociation product, since further ion etching simply results in a further loss of intensity from the carbonate features, and a complementary increase in intensity from the new oxygen feature. The extent of decomposition at any given ion dose may be related to the thermochemical properties of the parent carbonate. Implications of the work in the interpretation of sputter-depth profiles of such systems are discussed. A B Christie et al, Vacuum, 31 (10-12), 1981, 513-517. 35 5380. The oxygen effect in the growth kinetics of platinum silicides. (USA) Silicide formation is strongly affected by the presence of oxygen contained in the metal film. A study has been performed by heating at various times and temperatures samples constituted by a thin Pt film sputter deposited on a silicon substrate. Four different oxygen concentrations were implanted in the Pt film ranging from 1 to 0.1 atm?/o. The presence of oxygen slows down the growth rate of Pt2Si. At 315°C in the sample with an oxygen concentration of I atm%, about 1000 A of Pt2Si are formed after 20 min of annealing. During the silicide formation, the oxygen originally contained in the platinum films segregates at the Pt28i/Pt 771