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We measure the response of silicon photodiodes to irradiation by H/sup +/, He/sup +/, C/sup +/, N/sup +/, O/sup +/, Ne/sup +/, and Ar/sup +/ ions with energies up to 60 keV. The unique properties of these photodiodes, including an ultrathin SiO/sub 2/ dead layer and 100% internal carrier collection efficiency, allow direct measurement of the total energy lost to nuclear (nonionizing) and electronic (ionizing) energy loss processes, which are important for quantifying effects such as damage and charge deposition. When plotted as a function of E/mZ/sup 1/2/, where E, m, and Z are the incident ion energy, mass, and atomic number, respectively, the responsivity is found to follow a single curve that represents all ion species and energies used in this study. This enables rapid, accurate estimation of damage and charge deposition by an ion as a function of penetration depth in silicon. A comparison of the measurements with the stopping and range of ions in matter (SRIM) Monte Carlo simulation code shows that SRIM significantly overestimates the fraction of the incident energy lost to electronic stopping processes for E/mZ/sup 1/2/

We have studied the excitation of plasmons produced by 100 eV He + , Ne + and Ar + and by 5–100 keV H + and He + projectiles in Al and Mg through the observation of electrons from plasmon decay, ejected from clean and cesiated surfaces. At low velocities, plasmon excitation occurs only for ions of high potential energy and is independent of velocity. The effect of Cs adsorption on this potential plasmon-excitation mechanism on Al surfaces suggests that the excited plasmons are not bulk plasmons, as was assumed previously, but short-wavelength surface plasmons. For ions moving faster than a threshold velocity v th ∼1.3 v Fermi predicted by electron gas theories, kinetic plasmon excitation can occur because the valence electrons cannot respond instantaneously to screen the moving charge. We found that, contrary to theoretical expectations, plasmon excitation by H + and He + projectiles occurs below v th . With the aid of a simple model, we suggest that this sub-threshold excitation results from energetic secondary electrons.

We measure the change in the response of 100% internal carrier collection efficiency silicon photodiodes having 60 /spl Aring/ SiO/sub 2/ passivation layers due to the damage induced by bombardment with 10-60 keV ions of H, He, N, Ne, and Ar. We find an initially exponential decrease in responsivity with increasing ion fluence /spl Phi/ and use this to define a damage constant /spl beta/. The correlation of /spl beta/ with the nuclear stopping power of the incident ion instead of with the total energy lost to nuclear stopping indicates that damage in a channel lying within the n-type silicon near the Si-SiO/sub 2/ interface dominates the radiation-induced change in the photodiode response. We use a fluid model of electron transport in the channel to derive a universal curve to describe the damage as a function of ion fluence and to show that the damage constant /spl beta/ is proportional to the damage cross section. Over the energy range of this study, damage cross sections of N/sup +/, Ne/sup +/, and Ar/sup +/ are 10-100 times that of He/sup +/, and /spl sim/1000 times that of H.

Recent advances in solid-state detector (SSD) technology have demonstrated the detection of ions and electrons down to 1 keV. However, ions at keV energies lose a substantial amount of energy ΔN in a SSD through Coulombic interactions with target nuclei rather than through interactions that contribute to the SSD output pulse, whose magnitude is a measure of the ion’s incident energy. Because ΔN depends on the ion species, detector material, and interaction physics, it represents a fundamental limitation of the output pulse magnitude of the detector. Using 100% quantum collection efficiency silicon photodiodes with a thin (40–60 A) SiO2 passivation layer, we accurately quantify ΔN for incident 1–120 keV ions and, therefore, evaluate the detection limits of keV ions using silicon detectors.

Using silicon photodiodes with an ultrathin passivation layer, the average total energy lost to silicon target electrons (electronic stopping) by incident low energy ions and the recoil target atoms they generate is directly measured. We find that the total electronic energy deposition and the ratio of the total nuclear to electronic stopping powers for the incident ions and their recoils each follow a simple, universal representation, thus enabling systematic prediction of ion-induced effects in silicon. We also observe a velocity threshold at 0.05 a.u. for the onset of electronic stopping.