The production of stable vacancy-related point defects in silicon irradiated with 1.3 MeV protons has been studied as a function of ion flux (protons s-' cm-'), while keeping the total fluence constant. Since the total fluence was very low (5 x lo9 protons cm-'), no interference between neighboring ion tracks was expected. The defect concentrations have been measured by deep-level transient spectroscopy, and a decrease in the resulting defect density is found for increasing flux. This effect was unexpected and shows that there is an overlap between ion tracks, in spite of the low fluence. The behavior is attributed to the rapidly diffusing silicon interstitials, which overlap the vacancy distributions produced in adjacent ion tracks. When the ion flux is low, the distribution of vacancies from one ion becomes diluted and recombination with interstitials from ions impacting at a later time is rare. As the flux is increased the vacancy distribution from one ion will still be confined to a small volume when it is overlapped by interstitials from a later ion, leading to an increased recombination of vacancies and interstitials. Thus, within this low-fluence regime, the total concentration of stable vacancy-related defects decreases for a high flux. This result is supported by computer simulations of the defect generation kinetics.

Si(lOO) samples have been implanted with low does (10 7 -10 9 cm -2 ) of MeV 76 Ge and ,20 Sn ions. Deep level transient spectroscopy was used for sample analysis, and the generation of vacancy-related point defects is found to increase with increasing implantation temperature and to decrease with increasing ion dose rate. These results are in direct contrast to that for damage buildup at high doses (> 10 12 cm ~2), and the effect is attributed to rapidly diffusing Si self-interstitials which overlap and annihilate vacancies created in adjacent ion tracks.PACS numbers: 61.72. Bb, 61.72.Tt, 61.80.Jh, 71.55.Ht Implantation of energetic ions into crystalline semiconductors gives rise to atomic displacements and structural defects. The generation of stable defects depends on several parameters, e.g., ion energy, ion mass, sample temperature, ion dose, and dose rate. A process of crucial importance for damage buildup in semiconductors is defect annealing during implantation [1][2][3][4]. Usually, one distinguishes between two types of annealing processes during ion implantation [5]: (i) thermal or bulk annealing and (ii) dynamic annealing. Type (i) resembles ordinary thermal annealing and is caused by a rise in target temperature during high dose rate ion bombardment. In the following, we will concentrate on type (ii), and in particular, its dependence on dose rate and sample temperature.For doses above ~10 12 cm -2 and dose rates in the range of ~10 n to 10 15 cm~2s _i it is well established that the influence of dynamic annealing in semiconductors decreases with increasing dose rate and decreasing target temperature [1-6]. Alternative explanations exist for these effects [5,6] and one among others is that at sufficiently high dose rates, collision cascades can overlap before the single cascade defects have completed their annealing process [5]. As a result, a higher concentration of defects which are more stable at (and above) room temperature (RT) is formed. At low enough target temperatures the mobility of migrating defects responsible for the annealing process decreases, and the ion-induced damage is to a large extent "frozen in" [4]. Again, a high concentration of stable defects is generated in the single cascades as dynamic annealing diminishes.Recently, Hallen et al. [7] irradiated silicon at RT with 1.3 MeV protons using a dose of only 5xl0 9 cm -2 and dose rates of 10 7 to 10 10 cm~2s _1 . In direct contrast to the results for heavier ions and higher doses and dose rates, they found a reverse dose rate dependence; i.e., for a constant dose the resulting defect density decreased with increasing dose rate.In this work silicon samples have been implanted with low doses of MeV 76 Ge and 12° Sn ions using different dose rates and sample temperatures. To the best of our knowledge, we have observed for the first time a "reverse" temperature and dose rate dependence for point defect production by heavy ions in silicon. Indeed, the generation rate of divacancy centers (V2) is reduced by a factor of -2 as the impla...

High resolution Rutherford backscattering and channeling has been used to study the formation of surface oxides during room temperature bombardment of silicon with oxygen in a secondary ion mass spectrometry system. Stoichiometric SiO2 is formed at angles of incidence (to the surface normal)≤25° and the angular dependence is adequately modeled using the profile code. A linear dependence of oxide thickness on energy is obtained in the energy range 3–40 keV (per oxygen ion) and this is consistent with trim code calculations. The suboxide damage has also been measured and studied during annealing. Our data are consistent with a simple model of oxygen build up and formation of strong Si–O bonds during room temperature bombardment. Once a buried SiO2 layer is reached and Si bonds are saturated, oxygen can migrate in SiO2 to extend the oxide towards the surface.

Adsorption, diffusion, dewetting, and entrapment of acetone on Ni (111), surface-modified silicon, and amorphous solid water studied by time-of-flight secondary ion mass spectrometry and temperature programmed desorption

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