10 research outputs found
Investigation of high resistivity p-type FZ silicon diodes after 60Co {\gamma}-irradiation
In this work, the effects of Co -ray irradiation on high
resistivity -type diodes have been investigated. The diodes were exposed to
dose values of 0.1, 0.2, 1, and \SI{2}{\mega Gy}. Both macroscopic (--,
--) and microscopic (Thermally Stimulated Current~(TSC)) measurements
were conducted to characterize the radiation-induced changes. The investigated
diodes were manufactured on high resistivity -type Float Zone (FZ) silicon
and were further classified into two types based on the isolation technique
between the pad and guard ring: -stop and -spray. After irradiation, the
macroscopic results of current-voltage and capacitance-voltage measurements
were obtained and compared with existing literature data. Additionally, the
microscopic measurements focused on the development of the concentration of
different radiation-induced defects, including the boron interstitial and
oxygen interstitial (BO) complex, the carbon interstitial
and oxygen interstitial CO defect, the H40K, and the
so-called I. To investigate the thermal stability of induced
defects in the bulk, isochronal annealing studies were performed in the
temperature range of \SI{80}{\celsius} to \SI{300}{\celsius}. These annealing
processes were carried out on diodes irradiated with doses of 1 and
\SI{2}{\mega Gy} and the corresponding TSC spectra were analysed. Furthermore,
in order to investigate the unexpected results observed in the -
measurements after irradiation with high dose values, the surface conductance
between the pad and guard ring was measured as a function of both dose and
annealing temperature
Investigation of the Boron removal effect induced by 5.5 MeV electrons on highly doped EPI- and Cz-silicon
This study focuses on the properties of the BO
(interstitial Boron~-~interstitial Oxygen) and CO
(interstitial Carbon~-~interstitial Oxygen) defect complexes by
\SI{5.5}{\mega\electronvolt} electrons in low resistivity silicon. Two
different types of diodes manufactured on p-type epitaxial and Czochralski
silicon with a resistivity of about 10~cm were irradiated with
fluence values between \SI{1e15}{\per\square\centi\meter} and
\SI{6e15}{\per\square\centi\meter}. Such diodes cannot be fully depleted and
thus the accurate evaluation of defect concentrations and properties
(activation energy, capture cross-section, concentration) from Thermally
Stimulated Currents (TSC) experiments alone is not possible. In this study we
demonstrate that by performing Thermally Stimulated Capacitance (TS-Cap)
experiments in similar conditions to TSC measurements and developing
theoretical models for simulating both types of BO
signals generated in TSC and TS-Cap measurements, accurate evaluations can be
performed. The changes of the position-dependent electric field, the effective
space charge density profile as well as the occupation of the
BO defect during the electric field dependent electron
emission, are simulated as a function of temperature. The macroscopic
properties (leakage current and ) extracted from current-voltage
and capacitance-voltage measurements at \SI{20}{\celsius} are also presented
and discusse
Effects of Potassium Adsorption and PotassiumâWater Coadsorption on the Chemical and Electronic Properties of nâType GaN(0001) Surfaces
The
interaction of n-type GaN(0001) surfaces with potassium and
water is investigated using photoelectron spectroscopy, with special
focus on adsorbateâsubstrate charge-transfer processes and
water dissociation. Potassium atoms adsorb at the surface, forming
a distinct surface dipole layer. For very low K coverage, the attached
ionized K adsorbates result in a drop of the work function and the
released electrons induce a reduction of the initial upward band bending.
After stabilization of both quantities in the sub-monolayer regime,
a reverse effect is observed for higher K coverage up to one monolayer
(ML), exceeding the upward band bending of the clean surface. If the
K-covered surface is exposed to water, hydroxyl groups are formed,
whereas during long K and H<sub>2</sub>O coadsorption, a potassium
hydroxide film grows. In both cases, a further reduction of the work
function and an abrupt change in the surface depletion layer is recorded.
For the coadsorption, initially an electron accumulation layer forms
at the surface, approaching flat band conditions for higher KOH thickness.
Overall, the surface band bending can be drastically modified in the
range between +0.5 and â0.6 eV. These observations clearly
show that the electron density at the GaN(0001) surface can be reversibly
tuned by alkali-based adsorbates. Different reactions are observed,
which are directly linked to the charge-transfer processes and chemical
reactions induced by the K 4s electrons
Defect characterization studies on 60Co gamma-irradiated p-type Si diodes
Trabajo presentado al 40th RD50 Workshop on Radiation hard semiconductor devices for very high luminosity colliders, celebrado del 21 al 24 de junio de 2022 en el CERN (Zurich).Boron-doped silicon devices used in high radiation environment like the HL-LHC show a degradation in device performance due to the radiation induced deactivation of the active boron dopant. This effect is known as the so-called Acceptor Removal Effect and depends on particle type, energy and radiation dose. Here we present defect characterization studies using TSC (thermally stimulated current technique) and DLTS (Deep Level Transient Spectroscopy) to correlate radiation induced changes in the macroscopic device properties with the formation of microscopic defects. The defect spectroscopy techniques provide us information about defect characteristics such as activation energy, capture cross section and defect concentrations, and were performed
on 60Co gamma-irradiated B-doped silicon EPI-diodes of different resistivity.Peer reviewe
Defect characterization studies on neutron irradiated boron-doped silicon pad diodes and Low Gain Avalanche Detectors
High-energy physics detectors with internal charge multiplication, like Low Gain Avalanche Detectors (LGADs), that will be used for fast timing in the High Luminosity LHC experiments, have to exhibit a significant radiation tolerance. In this context, the impact of radiation on the highly boron-doped gain layer is of particular interest, since due to the so-called Acceptor Removal Effect (ARE) a radiation-induced deactivation of active boron dopants takes place, that is causing a progressive loss in the gain with increasing irradiation level. In this paper we present defect-spectroscopy measurements (Deep-Level Transient Spectroscopy and Thermally Stimulated Current technique) on neutron, proton and electron irradiated p-type silicon pad diodes of different resistivity as well as LGADs neutron irradiated at fluences up to 1Ă1015 neq/cm2. We show that compared to silicon pad diodes the determination of LGAD defect introduction rates is less straightforward as they are strongly influenced by the impact of the gain layer. The measured gain layer capacitance has a strong frequency and temperature dependence which makes DLTS measurements challenging to perform with results difficult to interpret. With the TSC technique the defects formed in the LGADs are nicely observed and can be compared to the defects formed in the silicon pad diodes. However, the exact assignment of defects to the gain layer or bulk region remains challenging and the charge amplification effect of the LGADs impacts the exact determination of defect concentrations. We also demonstrate that, depending on the TSC measurement conditions, defect induced internal electric fields are built up in the irradiated LGADs which impact the signal current. âąPresentation of defect spectroscopy studies (DLTS, TSC) on irradiated LGADsâąSignificant impact of the highly doped gain layer on the defect spectroscopy resultsâąMeasured gain layer capacitance shows strong frequency and temperature dependenceâąDefect induced internal electrical fields can be built up in irradiated LGADsâąBiOi introduction rates for neutron, electron and proton irradiated diodes are givenHigh-energy physics detectors, like Low Gain Avalanche Detectors (LGADs) that will be used as fast timing detectors in the High Luminosity LHC experiments, have to exhibit a significant radiation tolerance. Thereby the impact of radiation on the highly boron-doped gain layer that enables the internal charge multiplication, is of special interest, since due to the so-called Acceptor Removal Effect (ARE) a radiation-induced deactivation of active boron dopants takes place. In this paper we present defect-spectroscopy measurements (Deep-Level Transient Spectroscopy and Thermally Stimulated Current technique) on neutron irradiated p-type silicon pad diodes of different resistivity as well as LGADs irradiated at fluences up to 1 x 10^15 neq/cm2. Thereby we show that while for the silicon pad diodes irradiated with electrons, neutrons or protons the determination of defect electronic properties and defect introduction rates is straightforward, DLTS and TSC measurements on LGADs are strongly influenced by the impact of the gain layer. It is shown that the measurability of the capacitance of the gain layer shows a strong frequency and temperature dependence leading to a capacitance drop in DLTS and non-reliable measurement results. With TSC defects formed in the LGADs can be very nicely observed and compared to the defects formed in the silicon pad diodes. However the exact assignment of defects to the gain layer or bulk region remains challenging and the charge amplification effect of the LGADs impacts the exact determination of defect concentrations. Additionally, we will demonstrate that depending on the TSC measurement conditions defect induced residual internal electric fields are built up in the irradiated LGADs that are influencing the current signal of carriers emitted from the defect states
Electrochemical lithiation of thin silicon based layers potentiostatically deposited from ionic liquid
Strategic R&D Programme on Technologies for Future Experiments - Annual Report 2021
This report summarises the activities and main achievements of the CERN strategic R&D programme on technologies for future experiments during the year 2021
Annual Report 2022
This report summarises the activities and main achievements of the CERN strategic R&D programme on technologies for future experiments during the year 202
Extension of the R&D Programme on Technologies for Future Experiments
we have conceived an extension of the R&D programme covering the period 2024 to 2028, i.e. again a 5-year period, however with 2024 as overlap year. This step was encouraged by the success of the current programme but also by the Europe-wide efforts to launch new Detector R&D collaborations in the framework of the ECFA Detector R&D Roadmap. We propose to continue our R&D programme with the main activities in essentially the same areas. All activities are fully aligned with the ECFA Roadmap and in most cases will be carried out under the umbrella of one of the new DRD collaborations. The program is a mix of natural continuations of the current activities and a couple of very innovative new developments, such as a radiation hard embedded FPGA implemented in an ASIC based on System-on-Chip technology. A special and urgent topic is the fabrication of Al-reinforced super-conducting cables. Such cables are a core ingredient of any new superconducting magnet such as BabyIAXO, PANDA, EIC, ALICE-3 etc. Production volumes are small and demands come in irregular intervals. Industry (world-wide) is no longer able and willing to fabricate such cables. The most effective approach (technically and financially) may be to re-invent the process at CERN, together with interested partners, and offer this service to the community
Annual Report 2023 and Phase-I Closeout
This report summarises the activities of the CERN strategic R&D programme on technologies for future experiments during the year 2023, and highlights the achievements of the programme during its first phase 2020-2023