Helena Castán

ORCID: 0000-0002-3874-721X
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About
Contact & Profiles
Research Areas
  • Semiconductor materials and devices
  • Ferroelectric and Negative Capacitance Devices
  • Advanced Memory and Neural Computing
  • Semiconductor materials and interfaces
  • Advancements in Semiconductor Devices and Circuit Design
  • Integrated Circuits and Semiconductor Failure Analysis
  • Electronic and Structural Properties of Oxides
  • Neuroscience and Neural Engineering
  • Silicon and Solar Cell Technologies
  • Copper Interconnects and Reliability
  • Semiconductor Quantum Structures and Devices
  • Thin-Film Transistor Technologies
  • Ferroelectric and Piezoelectric Materials
  • ZnO doping and properties
  • Transition Metal Oxide Nanomaterials
  • GaN-based semiconductor devices and materials
  • Acoustic Wave Resonator Technologies
  • Silicon Carbide Semiconductor Technologies
  • Electron and X-Ray Spectroscopy Techniques
  • Silicon Nanostructures and Photoluminescence
  • Multiferroics and related materials
  • Nanowire Synthesis and Applications
  • Advancements in Battery Materials
  • Iron oxide chemistry and applications
  • MXene and MAX Phase Materials

Universidad de Valladolid
2015-2024

University of Helsinki
2020

National Institute of Chemical Physics and Biophysics
2020

University of Tartu
2020

Rochester Institute of Technology
2020

Universidad de Granada
2014

Universidad Complutense de Madrid
2001-2009

Centro Nacional de Microelectrónica
1992

Universitat Autònoma de Barcelona
1992

Oxide–semiconductor interface quality of high-pressure reactive sputtered (HPRS) TiO2 films annealed in O2 at temperatures ranging from 600 to 900 °C, and atomic layer deposited (ALD) grown 225 or 275 °C TiCl4 Ti(OC2H5)4, 750 O2, has been studied on silicon substrates. Our attention focused the interfacial state disordered-induced gap densities. From our results, HPRS oxygen atmosphere exhibit best characteristics, with Dit density being lowest value measured this work (5–6 × 1011 cm−2...

10.1088/0268-1242/20/10/011 article EN Semiconductor Science and Technology 2005-09-14

In this work, the electrical characteristics of different atomic layer deposited high-permittivity dielectric films (Al2O3, HfO2, and a nanolaminate them), with physical thickness about 10 nm, are evaluated. An extensive capacitance-voltage current-voltage characterization at room temperature is carried out on metal-insulator-semiconductor structures fabricated p-type n-type silicon substrates Al as metal gate. HfO2 layers found to exhibit higher constant, but they suffer from largest...

10.1116/1.3532544 article EN Journal of Vacuum Science & Technology B Nanotechnology and Microelectronics Materials Processing Measurement and Phenomena 2011-01-01

A crucial step in order to achieve fast and low-energy switching operations resistive random access memory (RRAM) memories is the reduction of programming pulse width. In this study, incremental with verify algorithm (ISPVA) was implemented by using different widths between 10 μ s 50 ns assessed on Al-doped HfO 2 4 kbit RRAM arrays. The stability means an endurance test 1k cycles. Both conductive levels voltages needed for showed a remarkable good behavior along reset/set cycles regardless...

10.3390/electronics9050864 article EN Electronics 2020-05-23

Abstract Memristive devices have shown a great potential for non-volatile memory circuits and neuromorphic computing. For both applications it is essential to know the physical mechanisms behind resistive switching; in particular, time response external voltage signals. To shed light these issues we studied role played by applied ramp rate electrical properties of TiN/Ti/HfO 2 /W metal–insulator–metal switching devices. Using an ad hoc experimental set-up, current–voltage characteristics...

10.1088/1361-6463/acdae0 article EN Journal of Physics D Applied Physics 2023-06-02

An electrical characterization of Al2O3 based metal-insulator-semiconductor structures has been carried out by using capacitance-voltage, deep level transient spectroscopy, and conductance-transient (G-t) techniques. Dielectric films were atomic layer deposited (ALD) at temperatures ranging from 300 to 800 °C directly on silicon substrates an buffer that was grown in the same process 15 ALD cycles °C. As for single growth temperatures, leads lowest density states distributed away interface...

10.1063/1.2177383 article EN Journal of Applied Physics 2006-03-01

Intermediate band formation on silicon layers for solar cell applications was achieved by titanium implantation and laser annealing. A two-layer heterogeneous system, formed the implanted layer un-implanted substrate, formed. In this work, we present first time electrical characterization results which show that recombination is suppressed when Ti concentration high enough to overcome Mott limit, in agreement with intermediate theory. Clear differences have been observed between samples...

10.1063/1.4774241 article EN Journal of Applied Physics 2013-01-10

Amorphous or cubic thin films were grown from tris(2,3-dimethyl-2-butoxy)gadolinium(III), , and precursors at . As-deposited on etched (H-terminated) Si(100) exhibited better leakage current-voltage characteristics as well lower flatband voltage shift than substrates. Interface trap densities in /hydrofluoric acid (HF)-etched Si samples annealed rather high temperatures.

10.1149/1.2761845 article EN Journal of The Electrochemical Society 2007-01-01

Due to the high number of reachable conductance levels in resistive switching devices, they are good candidates implement artificial synaptic devices. In this work, we have studied control intermediate HfO2-based MIM capacitors using current pulses. The set transition can be controlled a linear way kind signal. potentiation characteristic is not affected by pulse length due filament formation takes place very short times. This behavior does allow identical pulses obtain characteristic....

10.1109/jeds.2020.2979293 article EN cc-by IEEE Journal of the Electron Devices Society 2020-01-01

Thin HfO2 films were grown by atomic layer deposition on chemical vapor-deposited large-area graphene. The graphene was transferred, prior to the of overlayer, bottom dielectric pregrown Si/TiN substrate. Either HfCl4 or Hf[N(CH3)(C2H5)]4 used as metal precursor for layer. O2 plasma-assisted process applied growing from also top To improve transfer, effects surface pretreatments as-grown and aged Si/TiN/HfO2 substrates studied compared. retained its integrity after plasma processes. Studies...

10.1021/acsanm.1c00587 article EN cc-by-nc-nd ACS Applied Nano Materials 2021-05-12

The dependence of the current in TiN/Ti/HfO2/W devices on temperature is investigated range from 78 K to 340 K. Resistive switching cycles at are conducted explore thermal filament configurations with different intermediate resistance states. less conductive states show an increase as rises, while fully formed displays a metallic-like behavior. A comprehensive model, based Stanford Model including series resistance, proposed and successfully validated by experimental data. interplay between...

10.1016/j.mssp.2024.108480 article EN cc-by-nc Materials Science in Semiconductor Processing 2024-05-04

We have analyzed the electrical properties and bonding characteristics of SiNx:H thin films deposited at 200 °C by electron cyclotron resonance plasma method. The show presence hydrogen bonded to silicon (at with ratio N/Si<1.33) or nitrogen (for where N/Si is higher than 1.33). In 1.38, content 6 at. %. For compositions which are comprised between N/Si=1.1 1.4, concentration remains below 10 N/Si=1.38 exhibited better values (resistivity, 6×1013 Ω cm; electric breakdown field, 3...

10.1063/1.366713 article EN Journal of Applied Physics 1998-01-01

Room temperature conductance transients in the SiNx:H/Si interface are reported. Silicon nitride thin films were directly deposited on silicon by low electron-cyclotron-resonance plasma method. The shape of varies with frequency at which they obtained. This behavior is explained terms a disorder-induced gap-state continuum model for interfacial defects. A perfect agreement between experiment and theory obtained proving validity model.

10.1063/1.119658 article EN Applied Physics Letters 1997-08-11

The electrical properties of HfO2-based metal–insulator–semiconductor capacitors have been systematically investigated by means I–V and C–V characteristics, admittance spectroscopy, deep level transient conductance transient, flat band voltage techniques. Attention is also given to the study temperature dependence leakage current. HfO2 films were grown on p-type silicon substrates atomic layer deposition using hafnium tetrakis(dimethylamide) as precursor, ozone or water oxygen precursors....

10.1116/1.4768167 article EN Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 2012-11-27

A thorough study of the admittance TiN/Ti/HfO2/W bipolar resistive memories [resistance random access memory (RRAM)] was carried out under different bias conditions and in a wide range ac signal frequencies. We demonstrate that continuum intermediate states can be obtained by applying appropriate dc waveforms. Cumulative writing erasing cycles were performed triangular voltage waveform increasing amplitude. The influence initial on variation real (conductance) imaginary (susceptance)...

10.1063/1.5024836 article EN Journal of Applied Physics 2018-09-25

In the attempt to understand behavior of HfO2-based resistive switching devices at low temperatures, TiN/Ti/HfO2/W metal–insulator–metal were fabricated; atomic layer deposition technique was used grow high-k layer. After performing an electroforming process room temperature, device cooled in a cryostat carry out 100 current–voltage cycles several temperatures ranging from “liquid nitrogen temperature” 350 K. The measurements showed semiconducting high and resistance states. state, hopping...

10.3390/electronics10222816 article EN Electronics 2021-11-17

An in-depth simulation and experimental study has been performed to analyze thermal effects on the variability of resistive memories. Kinetic Monte Carlo (kMC) simulations, that reproduce well nonlinearity stochasticity switching devices, have employed explain results. The series resistance transition voltages currents extracted from devices based TiN/Ti/HfO2/W stack we fabricated measured at temperatures ranging 77 K 350 K. We observed for all magnitudes analyzed was much higher low...

10.1016/j.chaos.2022.112247 article EN cc-by-nc-nd Chaos Solitons & Fractals 2022-05-30

Al / HfO 2 SiN x : H n -Si metal-insulator-semiconductor capacitors have been studied by electrical characterization. Films of silicon nitride were directly grown on n-type substrates electron cyclotron resonance assisted chemical vapor deposition. Silicon thickness was varied from 3 to 6.6 nm. Afterwards, 12 nm thick hafnium oxide films deposited the high-pressure sputtering approach. Interface quality determined using current-voltage, capacitance-voltage, deep-level transient spectroscopy...

10.1063/1.3013441 article EN Journal of Applied Physics 2008-11-01

The influence of the silicon nitride blocking layer thickness on interface state densities (Dit) HfO2/SiNx:H gate-stacks n-type have been analyzed. consisted 3 to 7 nm thick films directly grown substrates by electron-cyclotron-resonance assisted chemical-vapor-deposition. Afterwards, 12 hafnium oxide were deposited high-pressure reactive sputtering. Interface determined deep-level transient spectroscopy (DLTS) and high low frequency capacitance-voltage (HLCV) method. HLCV measurements...

10.1063/1.3391181 article EN Journal of Applied Physics 2010-06-01

HfO2 thin films were atomic-layer deposited using different-precursor partial pressures and at different growth temperatures on n- p-type silicon substrates. The effect of processing parameters film thickness the electrical quality oxide–semiconductor interface was studied. Deep-level-transient spectroscopy conductance-transient techniques revealed 3–10 × 1011 cm−2 eV−1 trap densities, somewhat dependent conditions. Charge trapping took place mainly between semiconductor defects located...

10.1088/0268-1242/19/9/013 article EN Semiconductor Science and Technology 2004-07-30

Thin solid films consisting of ZrO2 and Fe2O3 were grown by atomic layer deposition (ALD) at 400 °C. Metastable phases stabilized doping. The number alternating cycles varied in order to achieve with different cation ratios. influence annealing on the composition structure thin was investigated. Additionally, electrical magnetic properties studied. Several samples exhibited a measurable saturation magnetization most charge polarization. Both phenomena observed sample Zr/Fe ratio 2.0.

10.3762/bjnano.9.14 article EN cc-by Beilstein Journal of Nanotechnology 2018-01-10

In the attempt to form an intermediate band in bandgap of silicon substrates give it capability absorb infrared radiation, we studied deep levels supersaturated with titanium. The technique used characterize energy was thermal admittance spectroscopy. Our experimental results showed that samples titanium concentration just under Mott limit there a relationship among activation value and capture cross section value. This obeys well known Meyer-Neldel rule, which typically appears processes...

10.1063/1.4905784 article EN Applied Physics Letters 2015-01-12
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