Top PDF Ferroelectric HfO2 for Emerging Ferroelectric Semiconductor Devices

Ferroelectric HfO2 for Emerging Ferroelectric Semiconductor Devices

Ferroelectric HfO2 for Emerging Ferroelectric Semiconductor Devices

deposited. 5 nm of aluminum was finally evaporated. An attempt was also made using the sputter system without breaking the vacuum. However, during the development of the exposed resist, the Al layer was developed away, which could indicate a porous film. This may be because of the low power used to sputter Al. Without sufficient energy to coalesce, the atoms might just have simply hit the wafer and adsorbed, leading to a low quality film. Evaporated Al, on the other hand, has more thermal energy and the atoms can form a dense film. After the first lithography, 15 nm of TiN was sputtered on samples G and H and then lifted-off. Different methods and temperatures of annealing were tried on each sample: 1 h at 600 ◦ C in a nitrogen furnace, 20 sec at 850 ◦ C in RTA and 1 sec at 1000 ◦ C in RTA. The rest of the process is similar to sample D and the final devices schematic can be seen in Figure 6.6 .
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Overview of emerging nonvolatile memory technologies

Overview of emerging nonvolatile memory technologies

technology: Flash memory, ferroelectric random-access memory (FeRAM), magnetic random-access memory (MRAM), phase-change memory (PCM), and RRAM. Nonvolatile memory, specifically ‘Flash’ memory, which is characterized by a large-block (or ‘sector’) erasing mechanism, has been the fastest growing segment of the semiconductor business for the last 10 years. Some of these newer emerging technologies include MRAM, FeRAM, PCM, spin-transfer torque random-access memory (STT-RAM), RRAM and memristor. MRAM is a nonvolatile memory [10,22]. Unlike DRAM, the data is not stored in an electric charge flow, but by magnetic storage elements. The storage elements are formed by two ferromagnetic plates, each of which can hold a mag- netic field, separated by a thin insulating layer. One of the two plates is a permanent magnet set to a particular polarity; the other's field can be changed to match that of an external field to store memory. STT-RAM is an MRAM (nonvolatile) but with better scalability over traditional MRAM. The STT is an effect in which the orientation of a magnetic layer in a magnetic tunnel junction or spin valve can be modified using a spin- polarized current. Spin-transfer torque technology has the potential to make MRAM devices combining low current requirements and reduced cost possible; how- ever, the amount of current needed to reorient the magnetization is at present too high for most commer- cial applications. PCM is a nonvolatile random-access memory, which is also called ovonic unified memory (OUM), based on reversible phase conversion between the amorphous and the crystalline state of a chalcogen- ide glass, which is accomplished by heating and cooling of the glass. It utilizes the unique behavior of chalcogen- ide (a material that has been used to manufacture CDs), whereby the heat produced by the passage of an electric current switches this material between two states. The different states have different electrical resistance which can be used to store data. The ideal memory device or the so-called unified memory would satisfy simultan- eously three requirements: high speed, high density, and nonvolatility (retention). At the present time, such mem- ory has not been developed. The floating gate nonvola- tile semiconductor memory (NVSM) has high density and retention, but its program/erase speed is low. DRAM has high speed (approximately 10 ns) and high density, but it is volatile. On the other hand, SRAM has very high speed (approximately 5 ns) but limited from very low density and volatility. It is expected that PCM will have better scalability than other emerging tech- nologies. RRAM is a nonvolatile memory that is similar to PCM. The technology concept is that a dielectric, which is normally insulating, can be made to conduct through a filament or conduction path formed after ap- plication of a sufficiently high voltage. Arguably, this is a
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Modeling and Implementation of HfO2-based Ferroelectric Tunnel Junctions

Modeling and Implementation of HfO2-based Ferroelectric Tunnel Junctions

Silvaco is a semiconductor simulation tool used often in both academic and industry research. It has modules for process simulation, Athena, and electrical simulation of a simulated process, Atlas; though electrical simulations are more suited to transistor performance and related connections. In order to verify the proposed process design, from Section 5.3, it was simulated using Athena. The code is included in Appendix C and important figures are shown in this section. Importantly, the CMOS devices are shown in Figure 5.4, showing appropriate wells and junction depths for source/drain. The window opened in TEOS is shown to be appropriate for isolating ferroelectric to desired areas, shown in Figure 5.5 with SiO 2 substituted for HfO 2 since Athena does
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Negative Capacitance beyond Ferroelectric Switches

Negative Capacitance beyond Ferroelectric Switches

A number of alternative approaches, broadly considered subsets of “Steep Subthreshold devices”, are now being contemplated to achieved . Techniques that result in , also largely referred to as Landau switches 5 , are of great significance to technology, as they result in low operating voltages and thereby reduced power consumption of electronic circuits. Amongst such techniques, reported to date, the most promising for future technology nodes are ferroelectric FETs (FE-FETs) 6,7 , initiated by the pioneering work of Salahuddin and Datta in 2008 8 , though others, such as piezoelectric FETs 9,10 , nanoelectro-mechanical FETs (NEMFETs) 11–13 , and phase-
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Multiscale Simulations of Dynamics of Ferroelectric Domains

Multiscale Simulations of Dynamics of Ferroelectric Domains

forces. The electronic structure is calculated with the local density approximation (LDA) plus Hubbard U parameter as implemented in the QUANTUM-ESPRESSO [160] package. We use the 40-atom supercell as the reference structure. The Brillouin zone is sampled using a 4 × 4 × 4 Monkhorst-Pack k-point mesh [137]. We use norm-conserving pseudopo- tentials [112] generated using OPIUM [161] with a plane-wave energy cutoff of 50 Ry. The initial database contains the ground-state ferroelectric rhombohedral (R3c) structure, strained R3c structures, paraelectric rhombohedral (R ¯ 3c), strained R ¯ 3c structures, and ran- domly chosen orthorhombic structures with various lattice constants. The optimized force field obtained from each simulated annealing run is used to run both constant-volume and constant-stress MD simulations to generate equilibrium structures at various temperatures, the energies and atomic forces of which are then added to the fitting database. We also used the 109 ◦ domain wall structure found by Lubk et al. [162] in the database to ensure correct domain wall energies. The parameterization process is continued until the force field correctly reproduces the DFT energies and atomic forces of structures sampled by MD simulations.
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A domain wall theory for ferroelectric hysteresis

A domain wall theory for ferroelectric hysteresis

Preisach and generalized Preisach models have also been widely used to characterize hysteresis in ferroelectric materials. In their classical form, Preisach operators are constructed from linear com- binations of multivalued kernels [33]. The coecients for each kernel represent the input level and magnitude when switching occurs between two saturation states which dene the kernel. When used to quantify magnetic hysteresis, the kernel has been interpreted as representing diametrically oppo- site dipole congurations with the coecients interpreted as quantifying the eld inputs required for dipole switching and degree to which they switch at the points. While a similar interpretation can be made for ferroelectric processes, the techniques are more commonly considered as phenomeno- logical and hence provide a purely mathematical model for the process. Generalized Preisach or Krasnoselskii-Pokrovskii models dier through the choice of kernel. As detailed in [2], the classical Preisach operators are discontinuous with respect to both the parameters and time. This is allevi- ated in Krasnoselskii-Pokrovskii operators through the use of smooth ridge functions which provide an envelop of admissible families. We note that the construction of Krasnoselskii-Pokrovskii kernels through translations of ridge functions is quite similar in philosophy to the use of shifted anhysteretic curves employed in the models of Miller et al [38] and Zhang and Rogers [54].
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How to Model an Ising Ferroelectric System: Case of the Investigation of the Dielectrics Properties of a Nano-Octahedral Ferroelectric System

How to Model an Ising Ferroelectric System: Case of the Investigation of the Dielectrics Properties of a Nano-Octahedral Ferroelectric System

TIM and predict from a nano-octahedral system the dielectric properties of a sample considered in a large number with a comparative investigation of the influence of the transverse field and the exchange interaction on the dielectrics properties. One will investigate the polarizations, longitudinal susceptibilities and the hysteresis loops of a ferroelectric nano-octahedral system spin S=1/2 within the framework of the effective field theory with probability distribution technique. In the Section 2, one will present the model and formalism used for the transverse Ising model. Furthermore the effects of the external electric field, temperature, transverse field and exchange interaction on the dielectric properties are well discussed in detail in the Section 3.
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On Ferroelectric and Dielectric Properties of PbHAsO4 Crystal

On Ferroelectric and Dielectric Properties of PbHAsO4 Crystal

crystal successfully. Our results are much better since we have not decoupled the correlations at an early stage. We have decoupled them after double differentiation. Due to this we have obtained much better theoretical expressions to explain ferroelectric transition and dielectric properties of PbHAsO 4 crystal and similar other crystal. If wee

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Thermo Gravimetric Studies Of Ferroelectric Ceramic Pbbatio3

Thermo Gravimetric Studies Of Ferroelectric Ceramic Pbbatio3

is a newly designed ceramic material, synthesised via assisted solid state thermo chemical reaction method. It is a ferroelectric polycrystalline solid having particle size in nanometer range. It is a perovskite tragonal crystal system belonging to the family of barium titanate. Perovskite oxide ceramics are very significant in research field because their high dielectricity enable them to contribute in high storage capacitors and their good optical e them suitable candidates in imaging devices working within the infrared region of EM spectrum. Barium ) ceramics have been extensively studied during the last few decades because of its excellent electrical (Othman et al., 2014). is chemically and mechanically very stable, exhibits ferroelectric properties above room temperature, has Curie 2016), high dielectric at room temperature ≥1500, low and enormous band gap Barium titanate is used in density multilayer ceramic capacitors Ferroelectric Random Access Memory (FRAM), Dynamic Random Access Memory (DRAM), characteristic of piezoelectric can be used for microactuator and sensor, characteristic of polarizability can be used Nonvolatile Ferroelectric Random Access Memories The BaTiO 3 ferroelectric
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Measurement of Ferroelectric Films in MFM and MFIS Structures

Measurement of Ferroelectric Films in MFM and MFIS Structures

The ferroelectric tunnel junction is a relatively new class of ferroelectric memory, based on the concept of the memristor, that seeks to create ferroelectric memory in a compact 1C cell structure. In this approach, a ferroelectric layer thin enough to have appreciable tunneling current is sandwiched between two electrodes. The ferroelectric polarization state of the film is then used to modulate the tunneling barrier, in effect creating a resistor whose resistance is based on previously applied voltages [10]. If the ferroelectric film is composed of many domains of varying properties, such a device is able to exhibit a range of resistances between the two fully saturated polarization states - a property that is especially useful for providing weighting in neuromorphic applications. These devices have not been commercialized yet, but they have potential for use in the types of 3D crossbar memory architectures that are just now becoming mainstream [11].
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First-Principles and Molecular Dynamics Studies of Ferroelectric Oxides: Designing New Materials for Novel Applications

First-Principles and Molecular Dynamics Studies of Ferroelectric Oxides: Designing New Materials for Novel Applications

Coherent optical control over ultrafast molecular behavior including chemical reac- tions has been explored in recent years [91], spurred by the application of optimal control theory and related methods [107, 80] and by the development of femtosec- ond pulse shaping techniques [127, 129, 20] through which complex optical wave- forms have been crafted and optimized to induce specified molecular responses. Here, we propose and model theoretically the extension of coherent control to collective structural change. We show through numerical simulations that temporally shaped terahertz (THz) fields can be used to induce ferroelectric domain switching with ex- tensive control over the collective microscopic pathway from initial to final structure, in a coherent process that is very different from the conventional stepwise switching mechanism [124].
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Structural and Physical Properies of Y- doped BiFeO3  Material Prepared by Sol-gel Method

Structural and Physical Properies of Y- doped BiFeO3 Material Prepared by Sol-gel Method

bismuth ferrite samples [15-16]. With increasing in substitution ions, there is a change of Bi–O covalent bonds as a result of the decline in the stereochemical activity of the Bi lone electron pair and thus in long range ferroelectric order. If the mode frequency is governed by local factors, such as the force constant and ionic mass it will be proportional to (k/M) 1/2 , where k is the force constant and M is

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Single Walled Carbon Nanotube Dominated Micron Wide Stripe Patterned Based Ferroelectric Field Effect Transistors with HfO2 Defect Control Layer

Single Walled Carbon Nanotube Dominated Micron Wide Stripe Patterned Based Ferroelectric Field Effect Transistors with HfO2 Defect Control Layer

which is mainly caused by defect densities of SWCNT [21]. These results suggest that the memory window hysteresis (4.2 V) of ferroelectric FeFET is caused by both BNT polarization and densities of SWCNT defects. Figure 6a shows the leakage current-voltage characteris- tics of the BNT/HfO 2 and BNT film. As can be seen, the

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On the Urbach rule in SbSI ferroelectric
crystal 

On the Urbach rule in SbSI ferroelectric crystal 

Thus, in spite of more than 35 years of studies of the nature of optical absorption edge in SbSI ferroelectrics, the results are still contradictory and their explanation seems to be rather complicated. The present paper is aimed at studying the temperature behaviour of the absorption edge in ferroelectric SbSI and explaining it from the point of view of presence of various types of crystal lattice disordering.

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A domain model for ferroelectric hysteresis

A domain model for ferroelectric hysteresis

The model presented here addresses the characterization of hysteresis in ferroelectric materials as well as relaxor ferroelectrics employed at temperatures well below the Curie temperature. The model is based on the quantica- tion of energy dierences between the minimum energy anhysteretic polarization and the polarization observed in applications. The anhysteretic E - P curve is derived using the nonlinear constitutive relations developed by Hom and Shankar. Hysteresis eects are quantied through the computation of the average energy required to move domain walls across inclusions or pinning sites inherent to the material. The resulting quasistatic ferroelectric model is analogous to that developed by Jiles and Atherton for ferromagnetic materials.
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Integration of Ferroelectric Thin Films in Tunable Microwave Devices

Integration of Ferroelectric Thin Films in Tunable Microwave Devices

Ferroelectric materials have been long considered for frequency agile devices due to their strongly nonlinear field dependent permittivity which allows for resonant frequency tuning in devices based on LCR circuits [5]. Ferroelectric thin films present several advantages over conventional semiconductor materials that make them very attractive for high frequency tunable devices, including low loss, fast tuning speed, and small physical dimensions [94],[151],[95]. Due to these advantages, ferroelectric thin film have been explored for many high frequency devices, including those based on AlGaN/GaN high electron-mobility transistors (HEMT) [179], phase shifters [127],[170], and phased array antennas [171]. Though numerous authors have explored the possibilities for ferroelectric varactors and addressed a number of material property concerns, comparatively few have investigated the challenges associated with translating these prototypical concepts into system-compatible devices. Perhaps of greatest importance is an appreciation for several practicalities associated with X-band frequencies. Understanding these concerns is critical since the advantages of ferroelectric varactors become most pronounced (with regard to competing technologies) in the higher frequency regimes. In this report, the authors address one of these practical issues – the need to fabricate tunable ferroelectric varactors with C max
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Ferroelectric Ceramic

Ferroelectric Ceramic

The ferroelectric relaxor materials are technically important because it displays the wide variety of phenomena. These compounds have diffuse phase transition of perovskite structure as well as those of tetragonal tungsten bronze. A considerable attraction has been made to perovskite structure based materials due to rich diversity of their physical properties and possible applications in various technologies like memory storage devices, micro electromechanical systems, multilayer ceramic capacitors, and recently in the area of Opto-electronic devices [1]. These useful properties have most often been observed in lead-based perovskite compounds, such as PMN–PT, PNN–PZT, PLZT, etc [2-3].The properties of these lead based compounds are attributed to their relaxor behaviour, However these compositions have high volatility and high toxicity in nature, which is not good for mankind. These reasons made researcher’s to think about lead free materials which are environmental friendly have properties whose structure is perovskite and relaxor behaviour in lead free materials. Many lead-free materials with perovskite structure such as BaTiO 3 (BT), (Bi 1/2 Na 1/2 ) TiO 3 (BNT),
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Synthesis of nano-structured Bi1−xBaxFeO3 ceramics with enhanced magnetic and electrical properties

Synthesis of nano-structured Bi1−xBaxFeO3 ceramics with enhanced magnetic and electrical properties

method. Structural, morphological, magnetic and ferroelectric properties of the products were investigated systematically by employing X-ray diffraction, field emission scanning electron microscope, vibrating sample magnetometer as well as electrical evaluation techniques, respectively. The XRD results demonstrated distorted rhombohedral BiFeO 3 crystal structure

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Influence of Sintering Temperature on Densification, Structure and Microstructure of Li and Sb Co Modified (K,Na)NbO3 Based Ceramics

Influence of Sintering Temperature on Densification, Structure and Microstructure of Li and Sb Co Modified (K,Na)NbO3 Based Ceramics

PZT-based ceramics, it is noted that the key approach for improving the piezoelectric properties of KNN-based ceramics is to lower the ferroelectric tetragonal-ferroelectric orthorhombic[r]

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STRUCTURAL, ELECTRICAL AND MAGNETIC PROPERTIES OF Y[Li 0.5

STRUCTURAL, ELECTRICAL AND MAGNETIC PROPERTIES OF Y[Li 0.5

The magnetostrictional deformation of ferrite phase and piezoelectric effect of the ferroelectric phase is responsible for ME effect [Patankar (2001)]. The ME coefficient gradually increases with increasing magnetic field up to 640 Oe and thereafter decreases and attains saturation at higher fields. This is because in the spinel ferrite, the magnetostrictive coefficient reaches saturation at a certain value of magnetic field. Beyond saturation, the magnetostriction produces a constant electric field in the piezoelectric phase making the ME coefficient decrease with increasing magnetic field.
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