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In recent years titanium nitride is being considered as a very promising
plasmonic material for data storage applications as it exhibits a pronounced
plasmonic dipolar resonance and has high thermal stability. However, there is a
lack of research where higher order resonance modes are examined. We address
this here by performing angle dependent spectral transmission measurements
nanodisks arrays made from titanium nitride. The measurements show strong
polarization dependence with s-polarized light causing excitation of the
quadrupole and higher order resonance plasmonic modes. These higher order modes
are required for the state-of-the-art designs of near-field transducers. This,
together with its outstanding thermal properties, makes TiN a favourable
material for data storage applications.
In this work we explore the mechanisms responsible for Random Telegraph Noise
(RTN) fluctuations in HfOx Resistive Random Access Memory (RRAM)
devices. The statistical properties of the RTN are analyzed in many operating
conditions exploiting the Factorial Hidden Markov Model (FHMM) to decompose the
multilevel RTN traces in a superposition of two-level fluctuations. This allows
the simultaneous characterization of individual defects contributing to the RTN.
Results, together with multi-scale physics-based simulations, allows thoroughly
investigating the physical mechanisms which could be responsible for the RTN
current fluctuations in the two resistive states of these devices, including
also the charge transport features in a comprehensive framework. We consider two
possible options, which are the Coulomb blockade effect and the possible
existence of metastable states for the defects assisting charge transport.
Results indicate that both options may be responsible for RTN current
fluctuations in HRS, while RTN in LRS is attributed to the temporary screening
effect of the charge trapped at defect sites around the conductive filament.
Feasibility of multiwavelength Raman spectroscopy was studied as a potential
in-line monitoring technique for grain size distribution in channel poly-Si used
in three dimensional stacked NAND (3D NAND) Flash memory devices. Various
channel poly-Si materials in 3D-NAND Flash memory devices, converted from
chemical vapor deposition (CVD) grown a-Si, were characterized using
non-contact, multiwavelength Raman spectroscopy and high resolution
cross-sectional transmission electron microscopy (HRXTEM). The Raman
characterization results were compared with HRXTEM images. The correlation
between the grain size distribution characterized by multiwavelength Raman
spectroscopy and “on current” (ION) of 3D NAND
Flash memory devices was investigated. Good correlation between these techniques
was seen. Multiwavelength Raman spectroscopy is very promising as a
non-destructive in-line monitoring technique for grain size distribution in
channel poly-Si used in 3D NAND Flash memory devices.
Reversible changes in the conductivity of HfO2 dielectric film between
high and low resistive states of a metal-insulator-metal memory cell were
attributed to the formation of oxygen vacancies and their clustering across the
insulator layer. In this study we present an innovative model which includes
generation of two-charged states of oxygen vacancies at the anode, their
diffusion to the cathode, transformation to one-charged state, and then to
neutral vacancies. Vacancy clusters in the insulator layer are built from only
neutral vacancies, while the kinetics of the clustering process is controlled by
diffusion of mobile one-charged state vacancies. Resistive switching is treated
as the formation of critical size vacancy cluster which provides continuous
conductive path through the dielectric layer. Good agreement between the
experimental data and the theoretical bias and temperature dependences for the
delay time was obtained.
Surface smoothing of Ru used as underlayer of magnetic tunneling junctions (MTJ)
in magneto-resistive random access memory (MRAM) was carried out with gas
cluster ion beam (GCIB) in order to improve device characteristics. For Ru
films, surface smoothing with 5 kV N2-GCIB irradiation was effective,
and CoFe films deposited on smoothed Ru surface also showed smooth surface. From
the hysteresis loop measurements of MTJ formed on smoothed Ru with
N2-GCIB, it showed improvement of inter-layer coupling magnetic field
(Hin) with decreasing the surface roughness of underlayer Ru. It
is expected that surface roughness of MgO in MTJ was also improved by smoothing
of underlayer Ru with N2-GCIB.
Effects of defect on ferroelectric stability in PbTiO3 (PTO) thin
films have been investigated using molecular dynamics with first-principles
effective Hamiltonian. In this paper, oxygen vacancy (Vo) has been considered to
study the hysteresis loop, spontaneous polarization as a function of film
thickness. Vo has been modeled as a charged point defect. Density functional
theory (DFT) calculations are performed to determine the Vo-induced localized
fields (both mechanical and electrical) and the calculated DFT results are used
as inputs to molecular dynamics simulations in a large system. The strain field
induced by the Vo is calculated by DFT calculations and fitted by the continuum
strain modeling, and the electrostatic field is given by the superposition of
the Vo-induced field and the external field. Vo significantly reduces the
spontaneous polarization and increases the critical thickness.
We fabricated ferroelectric (Pb,La)(Zr,Ti)O3 (PLZT) capacitors with
Sn:In2O3 (ITO) or Pt top electrodes and investigated
the ferroelectric properties of these PLZT capacitors. The shape of
polarization–voltage hysteresis loops was essentially unchanged and
the decrease in the remnant polarization of the ITO/PLZT/Pt capacitors was
smaller than that of the Pt/PLZT/Pt capacitors after annealing with 3%
D2 (in N2) at 200°C and 1 Torr
(i.e., FGAD). Time of flight
secondary mass spectrometry revealed that the D atoms were incorporated into the
PLZT film of the Pt/PLZT/Pt capacitors after 3% D2 annealing,
resulting in a decrease in the ferroelectric properties. In comparison, no D ion
signal was detected in the PLZT film after FGAD for ITO/PLZT/Pt
Topological (GeTe)/(Sb2Te3) superlattices (SL) are of
practical interest for memory applications because of different mechanism of
electric conductance switching in the crystalline phase. In the work, electrical
switching behavior of individual SL grains was examined employing a multimode
scanning probe microscope (MSPM) in a lithography mode at room temperature.
Using programmed bias voltage with different amplitude and pulse duration, we
observed the position-dependent variations of the switching voltage and the
current injection delay for [(GeTe)2
(Sb2Te3)]4 SLs on Si(100). The results shed
a light on the role of electric field and hot-electron injection on the SL