Radiation-induced Complexes Research Articles

Radiation and thermal formation of active centers in lithium and sodium fluorides

Results from the controlled formation of active centers in single LiF and NaF crystals using ionizing radiation are presented. New luminescence bands are observed in the spectral range of 500–1000 nm. The role of radiation-induced molecular complexes in the formation of new centers is discussed.

Estimation of Radiation-Induced Complex Concentration in CZ-Si by IR Absorption Spectroscopy

Radiation induced complexes in low carbon concentration, low electron dose Czochralski silicon crystal are examined by infrared absorption spectroscopy. By using the highly sensitive, highly accurate measurement and arithmetic procedures, carbon-oxygen(-self interstitial)and vacancy-oxygen complexes are detected in samples with carbon concentration about 1x1016 atoms/cm3 and electron dose about 1x1016 atoms/cm2. Also, their concentrations, are estimated by evaluating the relative oscillator strength. Quantitative analysis in high quality samples will provide important information on defect behavior in irradiated crystals.

Comparison of electron irradiation effect on thermal donors in Cz and oxygen doped FZ silicon

The effect of electron irradiation on n-type Cz- and oxygen-doped FZ-Si containing oxygen-related thermal donors (OTDs) due to a plasma hydrogenation and a subsequent thermal donor formation step at 450°C is investigated by capacitance–voltage (C–V) and deep level transient spectroscopy (DLTS) measurements. In order to explain the electron irradiation induced reduction of the carrier concentration, DLTS measurements were performed. They revealed the presence of thermal donors (TDs) and radiation-induced complexes. It is shown that the peak at EC−0.09eV related to OTDs in CZ-Si diode is not changed by the electron irradiation.

Enhancement of thermal donor formation in germanium by preliminary irradiation: infrared absorption measurements

Infrared absorption at 10 K of oxygen-rich Ge crystals after irradiation with fast electrons ( E=4 MeV, T≈100°C) and subsequent annealing at 220–420°C has been studied. It is found that upon heat-treatments of the irradiated samples at 220–280°C the simultaneous formation of four bistable thermal donors (TD1–TD4) occurs. This process is not accompanied by detectable changes in intensities of absorption bands at 780.4 and 818.0 cm −1, which are related to the oxygen dimer. Upon following anneals of the samples at 300–420°C, the strongly enhanced generation of the higher order TDs is observed with a simultaneous decrease in intensities of the bands originated from the oxygen dimer, TD1 and TD2. It is inferred that direct transformations of some radiation-induced defects into the first TD species occur in the irradiated samples. Radiation-induced complexes giving rise to local vibrational modes in the region 570–577 cm −1 and/or at 729, 733.5 and 745 cm −1 are suggested as possible precursors to the bistable TDs in Ge.

Distinctive features of the creation of radiation-induced defects in p-Si by photonassisted low-dose ion implantation

Deep-level transient spectroscopy (DLTS) was used to investigate how temperature and in situ photoexcitation affect the creation of radiation-induced defect complexes in p-Si during low-dose ion implantation. Samples of p-Si were simultaneously irradiated by Ar1 ions accelerated to 150 keV in doses of 7×1010 cm−2 and photoexcited with ultraviolet light at temperatures of 300 and 600 K. It was found that nonradiative heating of the samples by the implanted ions increases the total concentration of defect complexes while simultaneously changing the nature of the dominant complex. In contrast, ultraviolet illumination of the semiconductor suppresses defect formation. It was observed that in situ photoexcitation has a progressively smaller effect on the formation of radiation-induced defect complexes as the target temperature increases. The dependence of the concentration of secondary defects created as the accelerated ions are incorporated into the p-Si on the UV illumination intensity is found to be nonmonotonic. The results obtained for p-Si were analyzed and compared with previously known data for n-Si.

Characterization of Defects Created in Silicon Due to Etching in Low-Pressure Plasmas Containing Fluorine and Oxygen

AbstractDefect characterization in n-type silicon after the reactive ion etching (RIE) in low-pressure plasmas containing fluorine and oxygen is performed by using photoluminescence (PL) and deep level transient spectroscopies (DLTS). It is shown that RIE treatment results in the formation of (i) luminescence centers giving rise to the C- and G- excitonic lines and broad emission bands related to radiation-induced defect complexes and extended defects and (ii) several electron traps located at 0.16 eV, 0.26 eV, 0.43 eV and 0.58 eV below the conduction band. The addition of oxygen to the SF6 and CF4 plasma is shown to cause nonuniform stress in the near surface region. This stress is responsible for the experimentally observed splitting of the C- and G-excitonic lines, a low energy shift of the phosphorous bound exciton lines, as well as the splitting of the DLTS spectra. It is shown that the stress field is highly inhomogeneous across the wafer, and is rather related to the RIE-induced extended defects than caused by the reaction layer formed on the Si surface.

Behavior of implanted hydrogen in ferritic/martensitic steels under irradiation

The aim of this study was to clarify the behavior of hydrogen under irradiation in ferritic/martensitic stainless steel Fe-10Cr-2Mo-1Ni. Hydrogen was implanted into the specimens by ion accelerator or chemical cathodic charging method, followed by electron irradiation in a HVEM at temperatures from room temperature to 773 K. Streaks in the electron diffraction patterns were observed only during electron irradiation at 623–723 K. From these results it is suggested that the occurrence of the streak pattern is due to the formation of radiation-induced complexes of Ni or Cr with hydrogen along 〈100〉 directions.

Radiation damage and energy transfer in MnF2and RbMnF3crystals

Evidence is presented which indicates that radiation damage can be photochemically introduced in MnF2 and RbMnF3 crystals. At 77K radiation-induced defect-manganese complexes are formed which not only enhance the oscillator strength of the manganese optical transitions, but also act as terminal emission points for manganese excitons. Energy transfer to these defects occurs above 40K. The radiation-induced defects are shown to have annealing stages at 200K and about 300K in MnF2 and very little stable damage is found for 300K irradiations. On the other hand, the RbMnF3 300K irradiation does produce a significant amount of stable damage.