Irradiated Silicon Research Articles

A Two-Cycle Automated Approach to Electrical Resistivity Measurement of SiC Monitors for Peak Irradiation Temperature

An experimental system was designed and optimized to acquire real-time electrical resistance of the monitors during annealing. The system was then used to anneal irradiated silicon carbide (SiC) monitors. The altered resistance of the SiC monitors between the first heating cycle and the mean of the heating and cooling cycles that followed was found to significantly change when the annealing temperature exceeded the peak irradiation temperature. This was validated using nine irradiated SiC monitors annealed over two heating and cooling cycles. Of these SiC monitors, three were annealed for the first time. The remaining six monitors were already annealed, but four of these were found to contain residual defects that resulted in reasonable estimates of peak irradiation temperatures. Those estimated peak irradiation temperatures were statistically indifferent from the manual isochronal annealing method temperatures. The results demonstrate a preliminary potential for the two-cycle approach to replace or augment the current manual post-irradiation examination (PIE) process for extracting SiC monitor peak irradiation temperature.

Characterisation of irradiated and non-irradiated silicon sensors with a table-top two photon absorption TCT system

A tabletop Two Photon Absorption-Transient Current Technique (TPA-TCT) set-up built at CERN was used to investigate a non-irradiated PIN diode, an irradiated PIN diode, and a non-irradiated 5 × 5-multipad HPK LGAD. The intrinsic three dimensional spatial resolution of this method is demonstrated under normal incidence of the laser probe. A charge collection versus depth profile of the non-irradiated PIN diode is presented, where reflection on the rear silicon-air interface was observed. It is found that the time-over-threshold versus depth profile is particularly suitable to determine the boundaries of the DUT’s active volume. A depth scan of the irradiated PIN diode is discussed and a method to omit the single photon absorption background is presented. Finally, a charge collection measurement in the inter-pad region of the 5 × 5-multipad HPK LGAD is presented and it is demonstrated that TPA-TCT can be used to image the implantation and the electric field of segmented silicon devices in a three dimensional manner.

Advanced Crack Analytics on 3D X-ray Tomography of Irradiated Silicon Carbide Claddings

Advanced Crack Analytics on 3D X-ray Tomography of Irradiated Silicon Carbide Claddings

4D tracking: present status and perspectives

The past ten years have seen the advent of silicon-based precise timing detectors for charged particle tracking. The underlying reason for this evolution is a design innovation: the Low-Gain Avalanche Diode (LGAD). In its simplicity, the LGAD design is an obvious step with momentous consequences: low gain leads to large signals maintaining sensors stability and low noise, allowing sensor segmentation. Albeit introduced for a different reason, to compensate for charge trapping in irradiated silicon sensors, LGAD found fertile ground in the design of silicon-based timing detectors. Spurred by this design innovation, solid-state-based timing detectors for charged particles are going through an intense phase of R&D, and hybrid and monolithic sensors, with or without internal gain, are being explored. This contribution offers a review of this booming field.

Irradiated Silicon for Microwave and Millimeter Wave Applications

Complex permittivity measurements of irradiated high-resistivity float-zone silicon have been performed in this letter from microwave to millimeter-wave frequencies employing three different resonance techniques. It has been proven that the irradiated silicon exhibits resistivity of the intrinsic silicon at temperatures larger than 295 K and the loss tangent due to phonon absorption reaches about 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−5</sup> at room temperature. The total loss tangent of the room-temperature irradiated silicon is smaller than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$6\times10$ </tex-math></inline-formula> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−5</sup> at frequencies larger than 5 GHz. The real part of the complex permittivity of silicon linearly increases with temperature for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T $ </tex-math></inline-formula> > 200 K.

Investigation of the signal amplitude decrease in subsequent detection in irradiated silicon sensors

Upcoming high energy physics experiments like the High-Luminosity LHC require unprecedented radiation hardness of the detectors, as well as short readout time due to high luminosity and occupancy. Silicon has proven to be extremely radiation hard, sufficient signals can be recorded at fluences above 1×1016neq/cm2. The signal formation was studied in silicon strip sensors, which have been irradiated and annealed until the phenomenon of charge multiplication occurred. In previous studies it was observed that the detection of subsequent signals separated up to several microseconds is altered by the charge trapped during the proceeding pulses. In this paper, the investigation of the effects due to previously created charge in subsequent pulse detection is investigated. A decrease of signal pulse amplitude, which originates from effects of the flowing charges on the electric field configuration, is observed using irradiated diodes measured with top-TCT. The decrease can be explained by polarization, which is caused by trapped charges and is well known in larger band-gap materials like diamond, but often neglected for silicon at this relatively high temperature. The polarization mechanisms happening in the sensor are described by a theoretical model and additionally supported by simulations. The initial electric field and therefore the bias voltage, the time delay between subsequent pulses and the amount of initially created charge have a large impact on this phenomenon.

Investigation and correlation between surface modifications and field emission properties of laser-induced silicon plasma ion irradiated stainless steel

Laser-induced silicon (Si) plasma has been used as a source of ion irradiation for modifications in surface, structural and field emission properties of Stainless Steel (SS). Nd:YAG (532 nm, 10 ns) laser at irradiance of 15 GW/cm2 was used to generate Si-plasma ions which were detected by solid-state nuclear track detector (CR-39) and Faraday Cup (FC). Both the energy and fluence of Si ions were measured by FCs. In response to a stepwise increase in the number of laser pulses from 3000 to 12000, the ion fluence varies from 4.6 × 1014 to 18.3 × 1014 ions/cm2 with constant energy of 30 keV. Fourier Transformation Infrared (FTIR) spectroscopy analysis revealed that irradiated silicon makes the stretch band with oxygen Si–O–Si. X-Ray Diffraction (XRD) analysis confirmed the identification of new phase of Si (111) with an anomalous trend in crystallite size, dislocation line density and induced stresses in response to the irradiation with various Si ion fluences. Optical microscopy analysis showed the formation of pits, voids and tracks. Scanning electron microscope (SEM) analysis revealed the formation of nanoscale surface features including pores, craters, embedded particulates and protruded disk-like structures with multiple ablative layers at the fluence of 4.6 × 1014 to 13.7 × 1014 ions/cm2. At the highest ion fluence of 18.3 × 1014 ions/cm2, the flake/flower-like morphology is observed. Field emission (FE) properties were studied under ultra-high vacuum condition in a parallel plate configuration using planar virgin SS as an anode and structured SS as a cathode. The Fowler–Nordheim plots were obtained from I–V characteristics to evaluate the turn-on field, field enhancement factor β and a maximum current density ranging 1.5–4.5 V/µm, 5008–12807 and 96–454 nA/cm2, respectively. The variation in the FE properties is attributed to the different morphological features at varying silicon ion fluences.

Study of neutron irradiation effects in Depleted CMOS detector structures

In this paper the results of Edge-TCT and I-V measurements with passive test structures made in LFoundry 150 nm HV-CMOS process on p-type substrates with different initial resistivities ranging from 0.5 to 3 kΩcm are presented. Samples were irradiated with reactor neutrons up to a fluence of 2·1015 neq/cm2. The depletion depth was measured with Edge-TCT. The effective space charge concentration Neff was estimated from the dependence of the depletion depth on bias voltage and studied as a function of neutron fluence. The dependence of Neff on fluence changes with initial acceptor concentration in agreement with other measurements with p-type silicon. A long term accelerated annealing study of Neff and detector current up to 1280 minutes at 60°C was made. It was found that Neff and current in reverse biased detector behave as expected for irradiated silicon.

Time Resolution of an Irradiated 3D Silicon Pixel Detector

We report on the measurements of time resolution for double-sided 3D pixel sensors with a single cell of 50 μm × 50 μm and thickness of 285 μm, fabricated at IMB-CNM and irradiated with reactor neutrons from 8 ×1014 1MeV neq/cm2 to 1.0 ×1016 1MeV neq/cm2. The time resolution measurements were conducted using a radioactive source at a temperature of −20 and 20 °C in a bias voltage range of 50–250 V. The reference time was provided by a low gain avalanche detector produced by Hamamatsu. The results are compared to measurements conducted prior to irradiation where a temporal resolution of about 50 ps was measured. These are the first ever timing measurements on an irradiated 3D sensor and which serve as a basis for understanding their performance and to explore the possibility of performing 4D tracking in high radiation environments, such as the innermost tracking layers of future high energy physics experiments.

Boron-doped silicon: a possible way of testing and refining models of non-ionizing energy loss under electron- and proton irradiation

In this paper formation and annealing of boron-related defects in p-type silicon grown by the floating zone technique and subjected to electron and proton irradiation at room temperature are discussed. The defect model suggested earlier has provided fresh insight into the nature of two dominant complexes containing boron in irradiated p-Si, among them boron-divacancy complexes and interstitial boron-substitutional boron pairs. In the present work the same material is irradiated with 6 MeV electron and 8 MeV protons providing additional electrical data to test this model. Additionally new information on boron-related defects in heavily doped p-Si subjected to irradiation with 2.5 MeV electrons at 4.2 K and then subjected to isochronal anneals above room temperature is also discussed. The results obtained on proton irradiated p-Si(FZ) testify that the annealing behavior of boron-divacancy complexes appears to be complicated, in contrast to the behavior of substitutional boron-interstitial boron pairs. The defect model based on the experimental information furnished so far may be used for testing and refining computerized simulations of Non-Ionizing Energy Loss (NIEL) in irradiated silicon. Keywords: silicon, boron impurity, electron- and proton-irradiation, impurity-related complexes.

Plasma Deposition of Gallium Arsenide Nanoclusters on a Silicon Matrix

In the plasma state, a polar semiconductor gallium arsenide (GaAs) is deposited on a nonpolar silicon (Si) matrix in the &lt;111&gt; direction. Further qualitative and quantitative analyzes were carried out with the resulting GaAs/Si structure on a plasma‐beam device. We have chosen the optimal characteristics of this pulsed method for the deposition of GaAs from a plasma onto silicon (Si) created by a powerful ion beam. The optimal modes of the effect of temperature, electric field, and interval of pulse action on GaAs/Si quantum‐well heteronanostructures were considered. In the implementation of application of this structure in applied works related to opto‐ and nanoelectronics, active elements of solar cells require defect‐free compositions with ideal geometric parameters. Based on these experiments, the optimal mode of plasma influence on the formation of nanoclusters on the surface of the irradiated sample was chosen. SEM, EDS, and X‐ray diffraction analysis methods were used to determine such parameters as the structure, microhardness, phase and elemental composition of the irradiated Si silicon surface, as well as the penetration depth of GaAs deposited on a single‐crystal matrix. This work presents an experimental implementation of preparation of a gallium arsenide nanolayer and an applied theoretical analysis of the GaAs/Si heteronanostructure. We deposited gallium arsenide compounds from the plasma state on the surface of a silica crystal and studied the resulting structure by physicochemical methods.

Research on Ion Distribution and Stoping Power for Au Ions Irradiation Si, SiC

In order to predict the effect of heavy ion irradiation more accurately, the ion distribution and stoping power of Au irradiated silicon (Si) and silicon carbide (SiC) under various energy conditions were calculated by using SRIM program, and compared with the experimental values. It was found that the projeced range and divergence predicted by SRIM were significantly smaller, and the stopping power was significantly larger by about 25%. Therefore, the method of reducing the target density parameters was tried to make corrections. It was found that the gold ion distribution became deeper after the density decreased, the stopping power became smaller, and the curve was closer to the experiment with an error of only ~5%. The density reduction coefficient is introduced since there is no definite conclusion on how much density decreases. Based on a large number of previous experimental data, SRIM was used to calculate the density reduction coefficient values under different energy conditions repeatedly, and found that there is a corresponding relationship between the values and energy values. Finally, the polynomial regression fitting method was used to obtain their functional expressions, which laid a foundation for the prediction of Si and SiC irradiated by heavy ions.

Nanoindentation testing of Si3N4 irradiated with swift heavy ions

We report the results of the nanoindentation tests of silicon nitride irradiated with Ar (46 MeV), Kr (107 MeV), Xe (167 MeV, 220 MeV) and Bi (710 MeV) ions. The behaviour of hardness with respect to ion fluence was analyzed and correlated with the microstructure evolution examined using transmission electron microscopy. Insignificant changes in hardness are observed for ion species (Ar, Kr) for which the electronic stopping power is less than the threshold of latent track formation. Accumulation of latent tracks produced by Xe and Bi ions results first in hardening and then, after track region overlapping and amorphization of the crystalline matrix, in softening of irradiated silicon nitride.

Reductions in the thermal conductivity of irradiated silicon governed by displacement damage

We report on the measured thermal conductivity of silicon irradiated with an array of ions: ${\mathrm{C}}^{2+},$ ${\mathrm{N}}^{2+},$ ${\mathrm{Al}}^{2+},$ ${\mathrm{Si}}^{2+},$ ${\mathrm{P}}^{2+},$ and ${\mathrm{Ge}}^{2+}$. Results are analyzed in consideration of ion mass, radius, and induced displacement damage. Recrystallization of select samples via annealing demonstrates that structural disorder imparted by incident ions, rather than the ions themselves, drive the reduction in thermal conductivity. This, in turn, is dictated by the mass of the ion. A generalized model is provided to relate thermal conductivity to displacement damage. Knowledge of the displacements-per-atom profile can thus be used to predict thermal conductivity reduction for silicon devices in extreme environments.

Emergence of triangular features on ion irradiated silicon (100) surface

Low-energy off-normal Ar+ ion irradiation induces triangular features superimposed by nanoscale ripple patterns on Si (100) surface. Within the ion beam parameters range reported here, triangular features appear and show stronger lateral dependency on angle of incidence. Simulations performed using non-linear continuum equation incorporating dispersion term develops similar triangular features observed experimentally. Tuning parameters r1 and α as described in reference (K.M. Loew, R.M. Bradley, Phys. Rev. E. 100 (2019) 012801) generate angle and fluence like effects as in experiments for the triangular features. Experiment and simulation confirm more triangular elevations than depressions and their number increases with incidence angle up to 67∘.

Channeling efficiency reduction in high dose neutron irradiated silicon crystals for high energy and high intensity beam collimation and extraction

The channeling process in bent silicon crystals are used since '70s to manipulate beams of high energy particles. During the last decade, several studies and experiments carried out by the UA9 Collaboration at CERN demonstrated the possibility to use bent crystals for beam collimation, extraction, focusing and splitting in particle accelerators. These crystals are subject to deterioration due to the interaction of the particles with the crystal lattice, degrading the beam steering performance. For this reason, robustness tests are crucial to estimate their reliability and operational lifetime. A ∼8% of reduction in channeling efficiency on crystals irradiated with 2.5·1021/cm2 thermal neutrons was measured and reported in this manuscript. Extrapolations to possible operational scenarios in high energy accelerators are also discussed.

Electron mobility dependence on neutron irradiation fluence in heavily irradiated silicon

An increase of neutron irradiation fluence caused a decrease of Si radiation detector efficiency that was exceptionally well seen at 1017 neutron/cm2 fluence when the observed I–V characteristic of p-n junction under forward bias and under reverse bias became similar. Therefore the investigation of free carrier mobility could be a key experiment to understand the change of heavily irradiated silicon. The electron mobility was investigated by magnetoresistance means in microstrip silicon samples at temperature range T = 200–276 K. The analysis included the free carrier scattering by phonons, ionized impurities, dipoles and clusters and a contribution of each process was found by fitting the mobility dependence on temperature. The analysis of experimental data clearly demonstrated that the applied model did not explain the mobility in the samples irradiated to the highest fluence. Therefore a new concept of carrier transport is needed, and, as a conclusion, it could be stated that Si irradiated above 1016 cm–2 fluence (and up to 1020 cm–2) is a disordered material with the clusters.

Controlled wetting properties of proton beam irradiated silicon nanowires

• Pre-irradiation and SAE etching are developed for the fabrication of KSiNWs, selectively. • Point defects by proton irradiation are responsible for the observed kink like structures. • CA of KSiNWs demonstrated a superhydrophobic limit of ~ 133° at higher fluence. • Theoretical fitting concludes that the water droplet on KSiNWs slashes in a slower approach. Kinked silicon nanowires (KSiNWs) were grown by silver assisted electroless (SAE) etching of proton beam irradiated silicon. The length and the aspect ratio of the KSiNWs were found to decrease with an increase in the ion fluence. The point defects produced during proton irradiation seem to be responsible for the observed kink like structures. The wetting property of these KSiNWs has been controlled by pre-ion irradiation treatment. The surface roughness of KSiNWs was correlated with the observed water contact angle. An increase in implantation fluence resulted in a large contact angle, approaching the superhydrophobic limit (~133°).

Microwave photoconductance decay measurements of n- and p-type silicon irradiated with neutrons and protons

N-type and p-type silicon were irradiated by neutrons and protons from low to high fluence range (108 − 1011 cm-2 for neutrons and 1010 − 1013 cm-2 for protons). The carrier recombination lifetime of each irradiated silicon was measured using a microwave photoconductance decay method, and the resistivity of the irradiated silicon was also measured. Both neutron and proton irradiation induced a similar lifetime at the same irradiation fluence. The defect formation rates were determined to vary with irradiation fluence from the inverse lifetime dependence on irradiation fluence. The sheet resistance was increased above a threshold fluence. The result shows that at least three different values of defect formation rate are present in the fluence range of 109 − 1015 cm-2, and it may have potential for practical use as low-dose dosimeters.

Effect of irradiation of silicon photodiode arrays for ITER radial x-ray camera investigated by measuring response and current-voltage characteristics.

The response and current-voltage (I-V) characteristics of irradiated and non-irradiated silicon photodiode arrays (SPDAs) for use in the International Thermonuclear Experimental Reactor camera are measured and compared. Irradiation experiments are carried out using a uranium-zirconium hydride pulsed reactor. The total equivalent 1MeV neutron fluence with energy above 0.01MeV is ∼9.89 × 1013ncm-2. The output signal of the irradiated SPDA (XD2) shows a nonlinear trend during the irradiation experiment. The final signal is about 5.6% of the original one in the visible light region. Tests on the Experimental Advanced Superconducting Tokamak (EAST) show that the XD2 signal is 70%-80% of that of a non-irradiated SPDA (XD3). This indicates that irradiated SPDAs can still observe plasma radiation after exposure to 9.89 × 1013ncm-2 neutron fluence. However, because the neutron fluence of external camera detectors will reach 1.4 × 1016ncm-2 in D-T phase, the SPDAs might become unusable at some point. The responsivity ratio of irradiated and non-irradiated SPDAs is about 4%-20% from 7 to 13 keV. The degradation of responsivity is related to the energy level. After irradiation, the reversed dark current rises from 0.1 to 10 nA to a level of around 1 µA. In terms of tests of XD2 on EAST, zero bias is a good working condition for irradiated SPDAs.