A.M. Zaitsev

Defect production in silicon irradiated with 5.68 GeV Xe ions

Abstract Silicon irradiated by 5.68 GeV 129 Xe ions at fluences 5 × 10 11 , 5 × 10 12 and 5 × 10 13 cm −2 has been investigated by spreading resistance, EPR, optical absorption and X-ray diffraction techniques. The most damaged layer has been found at depths from 600 to 620 μm depending on the fluence, what coincides well with the TRIM-calculated projected range value R p = 616 μm. Deep tails of electrically active defects have been found beyond the projected range. The intensities and ranges of these tails increase with the irradiation fluence. No trace of amorphization has been detected by EPR for all the fluences. The observed peculiarities of the defect production and depth defect distribution by the energetic Xe ions lead to a conclusion that most point radiation defects are created predominantly by nuclear stopping whereas the formation of amorphous areas is strongly suppressed by electronic stopping power.

Peculiarities of damage in diamond irradiated by high energy ions

Abstract High energy copper (63 MeV, 5 × 10 14 cm −2 ) and neon (26.7 MeV, 5 × 10 14 cm −2 ) implantation of diamond crystals results in a single EPR line similar to that of paramagnetic centers (PC) of amorphous regions (AR) produced by low energy implantation but having marked anisotropy and asymmetry. The PC symmetry is axial with the axis coinciding with the ion beam direction. It has been shown that the damage regions produced in diamond by high energy ion irradiation are tracklike regions, stretched along the irradiation direction. It has been established that the cross-section geometry of these regions depends on the primary ion beam orientation relative to the crystal axes: the tracklike regions have the C ∞ -symmetry axis for the irradiation along the 〈111〉 direction and they have the C 4 -symmetry axis for the irradiation along the 〈100〉 direction. It has been proposed that within the tracklike regions the tetrahedral atom coordination is being lost and some sort of quasi-one-dimensional long-range ordering appears. A weak magnetic ordering is also proposed to be characteristic of these regions.

Ion track doping

Abstract Longitudinal dopant distribution along ion tracks in soft (polymers [1–5]) and hard (diamond [6,7]) condensed carbonaceous matter have been studied by neutron depth profiling and cathodoluminesence. Both in-diffusion from the aqueous phase and energetic ion implantation were used in primary track doping. In-situ self-decoration of tracks and post-implantation with a secondary ion species were used in the specific case of ion implantation. Radial dopant distributions were also studied by means of a modified tomographic procedure. Decorative doping of ion bombarded solids is useful in probing track structure, and especially in pointing the way to potential development of nanometric-sized electronic devices.

Defect production in silicon implanted with 13.6 MeV boron ions

Abstract EPR measurements, spreading resistance and optical reflectivity profilometry of silicon irradiated with 13.6 Me V boron ions within a dose range 10 13 to 2 × 10 15 cm −2 have been performed. It is shown that the defect production depends on both electronic and nuclear stopping powers and does not lead to the creation of amorphous layers but only precursors of the amorphous phase regions even at the highest dose 2 × 10 15 cm −2 . The asymmetrical profile of the electrically active implanted boron with a tail towards the bulk of the substrate is explained by channelling of swift ions through latent tracks. Point defects produced by high energy ion irradiation are found to be responsible for the increase of the chemical resistance of silicon in the irradiated layer.

Hydrogen passivation of the paramagnetic centers in amorphous regions of ion-implanted diamond☆

Abstract The effect of hydrogenation (j = 30 μA/cm2, E = 300 eV, T = 200°C) on the paramagnetic centers (PC) in amorphous regions (AR) of phosphorus implanted (100 keV, 1.8 × 1015 cm−2) diamond is studied. The passivation of the vacancy type defects by hydrogen atoms have been analyzed in terms of the MO LCAO (CNDO/2) method on a cluster approach based on the example of vacancy and divancancy models. The calculations show that the saturation ofall dangling bonds with hydrogen atoms causes the total removal of the local levels from the band gap for the vacancy case and almost the total removal for the divancy case. The MO LCAO (CNDO/2) calculation of the interaction of hydrogen atoms with the intrinsic atoms in tetrahedral (T) interstitial sites modifies the structure of their electronic levels but passivation of these defects does not take place. The calculations predict that the T-interstitialcy can reveal donor properties. The activation energy of the defect level near the c-band reduces as a result of the interaction of this defect with hydrogen atoms. The experimental and theoretical results are in good agreement with a model of the isotropic EPR signal formation in amorphous diamond. The main idea of this model is that the exchange interaction between point paramagnetic defects and/or motion of spin carriers simultaneously with the disordering of crystal structure results in a transformation of multicomponent anisotropic spectra of these defects to one isotropic line. The contribution of vacancy-type defects to the formation mechanism proposed predominates.

Penetration of high energy ions in semiconductors through tracks: simulation with transport equations

Abstract The effect of channeling of high energy ions through latent tracks in solids is described theoretically by means of transport equations. It is shown that deep tails in implanted impurity and radiation damage depth distributions by high energy ion implantation can be explained by this effect. The experimental data obtained for silicon and diamond implanted with high energy Ni, Kr, and Xe ions are compared with theoretical predictions.

EPR, XRD and optical reflectivity studies of radiation damage in silicon after high energy implantation of Ni ions

Abstract (111) silicon has been implanted with 6 MeV 68 Ni ions at various temperatures in a dose range from 5 × 10 12 to 2 × 10 17 Ni cm 2 . Quantitative depth resolved optical studies on the radiation damage are compared with EPR and XRD measurements, giving direct information on existing defect species and changes of the lattice period, respectively. Results of EPR investigations support the interpretation of the dose and temperature dependence of the optically detected damage given by Lindner and te Kaat [J. Mater. Res. 3 (1988) 1238], who base themselves on the damage model of Hecking et al. [Nucl. Instr. and Meth. B 15 (1986) 760]. EPR lines of five different point defect (Si-A4, Si-P1, Si-A6, Si-B2, Si-P3) and of amorphous material are observed. The use of different experimental methods allows for a comparison of the individual sensitivities for several kinds of damage.

Depth distributions of MeV-boron implanted into silicon

Abstract A model for calculation of the range distribution of energetic ions with taking into account the channeling effect is proposed. The measurement of the depth distributions of boron ions in silicon crystals implanted at 13.6 and 91 MeV revealed significant difference between the measured and the calculated range profiles when the channeling effects have not been included in the calculation. In spite of deminishing the critical angles of channeling with growing ion energy the probability of the capture of ions into the channeling regime is significant in case of high energy implantation even when the incident angles are 7–10° off the main crystallographic directions.

Molecular dynamics simulation of stable defect formation in Si via Coulomb explosion

Abstract Defect formation in semiconductors via stopping of high energy ions has been investigated by molecular dynamics simulation. A quantitative model of the Coulomb explosion process based on dielectric approach has been presented. A possibility to define the track formation by the density of the energy deposited in the Coulomb explosion SC and the properties of target has been shown. The most important simulation result is a very sharp SC threshold of the track formation, which has been determined for Si (45 eV/nm) and diamond (35 eV/nm) targets.

Diamond Based p-i-n Transistor

Diamond based semiconductor structure with an active insulating zone is a very perspective component of diamond electronics. The work of such device is based on space charge limited current (SCLC) or electron-hole recombination and space charge limited double injection current in insulator. The main advantage of the structure is, first of all, a lower concentration of defects in the dielectric active zone than in doped one, that allows to receive high mobility of the carriers ∼n diamond, and second, in elimination of restrictions, connected with deep acceptor level of B in diamond. P-i-M and p-i-n diodes, p-i-p structures, p-i-p field effect transistor (FET) with a Schottky barrier gate and p-i-p FET with a SiO2 gate insulator have been already developed and described [1–5]. Usage i-diamond as working area leads to the improvement of working parameters of active diamond devices. In p-i-p FET the holes are injected from p-diamond and transported by SCLC mechanism in the i-region. However currents of double injection significantly exceed SCLC [6]. One of the variants of high power insulated gate p-i-n transistor is described [7].