Erase Process Research Articles

Fully Optical Control of Polarization Current Direction in a Cyanide-Bridged Trinuclear Complex.

As a remote and non-contact stimulus, light offers the potential for manipulating the polarization of ferroelectric materials without physical contact. However, in current research, the non-contact write-read (erase) process lacks direct observation through the stable current as output signal. To address this limitation, we investigated the photoinduced polarization switching capabilities of the cyanide-bridged compound [Fe2Co] using visible light, leading to the achievement of rewritable polarization. By subjecting [Fe2Co] crystals to alternating irradiation with 785 nm and 532 nm light, the polarization changes exhibited a distinct square wave pattern, confirming the reliability of the writing and erasing processes. Initialization involved exposing specific crystal units to 532 nm light for storing "1" or "0" information, while reading was accomplished by scanning the units with 785 nm light, resulting in brief current pulses for "1" states and no current signal for "0" states. This research unveils new possibilities for optical storage systems, paving the way for efficient and rewritable data storage and retrieval technologies, such as the next-generation memories.

Fully Optical Control of Polarization Current Direction in a Cyanide‐Bridged Trinuclear Complex

As a remote and non‐contact stimulus, light offers the potential for manipulating the polarization of ferroelectric materials without physical contact. However, in current research, the non‐contact write‐read (erase) process lacks direct observation through the stable current as output signal. To address this limitation, we investigated the photoinduced polarization switching capabilities of the cyanide‐bridged compound [Fe2Co] using visible light, leading to the achievement of rewritable polarization. By subjecting [Fe2Co] crystals to alternating irradiation with 785 nm and 532 nm light, the polarization changes exhibited a distinct square wave pattern, confirming the reliability of the writing and erasing processes. Initialization involved exposing specific crystal units to 532 nm light for storing "1" or "0" information, while reading was accomplished by scanning the units with 785 nm light, resulting in brief current pulses for "1" states and no current signal for "0" states. This research unveils new possibilities for optical storage systems, paving the way for efficient and rewritable data storage and retrieval technologies, such as the next‐generation memories.

Statistical modeling of degradation behavior in Split-Gate Non-Volatile memory devices

A comprehensive modeling approach combining Kinetic Monte Carlo method and the Finite Element Method is presented in this study for simulating the degradation behavior of split gate non-volatile memory. The oxide layer between erase gate and floating gate is proved to be the weakest link, caused by the intensive electrical field enhancement during the erase process. The clustering effect shown by the simulated reading current distribution indicates the impact of process induced traps and corresponding early failures. Moreover, the simulation results of endurance test also show a good resemblance of the trends from experimental data. Based on both simulation and experimental data, the prediction of endurance limit regarding read reference level is provided. Our statistical modeling approach can be applied as a design for reliability tool, offering a comprehensive assessment of the reliability requirements for wide range of operating conditions and different layout schemes.

A Fast Weight Control Strategy for Programmable Linear RAM Based on the Self-Calibrating Erase Operation

Computing-in-memory (CIM) has attracted great attention due to the need for breaking through the “memory wall”. Programmable linear random-access memory (PLRAM) for high-precision weight control is proposed to tear down the wall. However, the slow programming algorithm to tune cells limits its application in multi-level memory. Herein, a fast weight control strategy for PLRAM based on the self-calibrating erase operation is presented. The unique sidewall tunneling oxide utilized in PLRAM for bi-directional Fowler–Nordheim tunneling results in the corner-enhanced poly-to-poly tunneling effect and the self-calibrating capability during the erase process. By adopting this strategy, the efficiency of weight tuning in the PLRAM array is improved by 51% compared with the current method. The worst case is 4.9 ms for erasure, which only needs to be verified 10 times. The improvement of weight tuning efficiency means further development in CIM for PLRAM and also shows the significant prospect of PLRAM used in multi-level memory.

Ag nanoparticles capped TiO2 nanowires array based capacitive memory

Glancing angle deposition technique was used to fabricate Ag nanoparticles (NPs) capped TiO2 Nanowire (NW) array structure for capacitive memory application. Electron microscopes confirmed the sandwiched structure of Ag NPs between TiO2 thin-film (TF) and NW. The average length of the vertical TiO2 NW and diameter of Ag NPs (with density ~ 1012 cm2) were found to be ~ 350 ± 5 nm and ~ 3.2 ± 0.4 nm, respectively. An enhanced photoluminescence was observed in case of Ag NPs capped TiO2 NWs due to the presence of high carriers as compared to bare TiO2 NW. The capacitance (C)–voltage (V) hysteresis was measured for both Ag NPs capped TiO2 NW and bare TiO2 NW at different sweeping voltage (± 3– ± 10 V) at 1 MHz frequency. A high capacitive memory window of 7.12 V was obtained for Ag NP capped TiO2 NW at ± 10 V with an excellent endurance upto 1000 cycle. Significantly lesser charge loss of 23% was obtained after a span of 104 s with a hole and electron loss of 10.6% and 17.8% respectively. The program and erase process in the device was explained with the help of a band diagram.

Floating-Gate Corner-Enhanced Poly-to-Poly Tunneling in Split-Gate Flash Memory Cells

The poly-to-poly tunneling characteristics in the third-generation SuperFlash memory cell have been analyzed. It has been demonstrated that, even without a sharp floating-gate (FG) tip, the cell still demonstrates the main features of the erase process from previous SuperFlash generations, namely, corner (tip)-enhanced tunneling, asymmetry of the tunneling voltage in forward and reverse directions, strong localization of the tunneling process, and effective suppression of anode hole injection. Furthermore, a new method for measuring the tunneling voltage on a regular FG cell is described. The reliability aspects of corner-enhanced tunneling in the SuperFlash cell are also discussed.

Reconstruction dynamics of recorded holograms in photochromic glass

We have investigated the dynamics of the record-erase process of holograms in photochromic glass using continuum Nd:YVO₄ laser radiation (λ=532 nm). A bidimensional microgrid pattern was formed and visualized in photochromic glass, and its diffraction efficiency decay versus time (during reconstruction step) gave us information (D, Δn) about the diffusion process inside the material. The recording and reconstruction processes were carried out in an off-axis setup, and the images of the reconstructed object were recorded by a CCD camera. Measurements realized on reconstructed object images using holograms recorded at a different incident power laser have shown a two-stage process involved in silver atom kinetics.

Temperature dependant flash memory erase transient simulation (Part II)

We present a detailed and accurate physics based transient simulation for modeling flash memory erasing at ambient and non-ambient temperatures. Typical cells are erased by moving electrons from the floating gate to the drain, source or substrate. Part 1 of this paper derives the equations used to model substrate erasing. This paper addresses drain erase modeling using a simulation based on the solution to Poisson’s equation with temperature as an independent variable. The goal of this paper is to demonstrate the derivation of an accurate erase simulation and show the effects of temperature on the threshold voltage during the erase process. Several papers have been published on this topic but fail to present detailed derivations and none using this exact set of equations to model the temperature dependent erasing process.

Temperature dependant flash memory erase transient simulation (Part I)

We present a detailed and accurate physics based transient simulation for modeling flash memory erasing at ambient and non-ambient temperatures. Typical cells are erased by moving electrons from the floating gate to the drain, source or substrate. Part I of this paper addresses substrate erase modeling using a simulation based on the solution to Poisson’s equation with temperature as an independent variable. The goal of this paper is to demonstrate the derivation of an accurate erase simulation and show the effects of temperature on the threshold voltage shift during the erase process. Several papers have been published on this topic but fail to present detailed derivations and none using this exact set of equations to model the temperature dependent erasing process.

Three-dimensional modeling of the tunneling potential in MOS memories embedded with metal nanoparticles

This paper undertakes a three-dimensional (3D) analysis of the electrostatic fields developed in non volatile SiO 2/HfO 2 memories (NVM) with metallic nanoparticles (m-NPs) embedded in the interface. Such a 3D approach is necessary in the case of m-NPs in contrast to the usual NVM based on Si NPs where a 1D analysis provides sufficient accuracy. The tunneling processes are then analyzed within this framework. It is concluded that the 3D potential will affect substantially the erase process at all voltages but in the charging process it will do so only at low voltages.

Small Molecular Organic Nonvolatile Memory Cells Fabricated with in Situ O2Plasma Oxidation

We developed small molecular organic nonvolatile 4F² memory cells using metal layer evaporation followed by O₂ plasma oxidation. Our memory cells sandwich an upper α-NPD layer, Al nanocrystals surrounded by Al₂O₃, and a bottom α-NPD layer between top and bottom electrodes. Their nonvolatile memory characteristics are excellent: the V th , V p (program), V e (erase), memory margin (I on /I off ), data retention time, and erase and program endurance were 2.6V, 5.3V; 8.5V, ?1.5×10², 1×10 5 s, and 1×10³ cycles, respectively. They also demonstrated symmetrical current versus voltage characteristics and a reversible erase and program process, indicating potential for terabit-level nonvolatile memory.

NON-VOLATILE HIGH SPEED & LOW POWER CHARGE TRAPPING DEVICES

We report the operational characteristics of ultra-small-scaled SONOS (below 50 nm gate width and length) and SiO 2/ SiO 2 structural devices with 0.5 um gate width and length where trapping occurs in a very narrow region. The experimental work summarizes the memory characteristics of retention time, endurance cycles, and speed in SONOS and SiO 2/ SiO 2 structures. Silicon nitride has many defects to hold electrons as charge storage media in SONOS memory. Defects are also incorporated during growth and deposition in device processing. Our experiments show that the interface between two oxides, one grown and one deposited, provides a remarkable media for electron storage with a smaller gate stack and thus lower operating voltage. The exponential dependence of the time on the voltage is reflected in the characteristic energy. It is ~0.44 eV for the write process and ~0.47 eV for the erase process in SiO 2/ SiO 2 structural device which is somewhat more efficient than those of SONOS structure memory.

Experimental analysis of tape noise

The mechanism of the tape medium noise is investigated by comparing the magnetization fluctuation resulting from an incremental DC erase process. It is found that the produced magnetization fluctuation displays contrasting behavior for recording heads with two very different gap lengths. A quantitative analysis of the medium noise mechanisms indicates that the sensitivity of the record head to spacing fluctuations explains these differences, and it is concluded that the main mechanism of the medium noise in advanced tape media is the head medium spacing fluctuation due to surface roughness.

Quantifying advanced tape medium noise

An investigation of the tape medium noise mechanism analyzed the magnetization fluctuation produced by an incremental dc erase process in a variety of modern metal-particle tape media. It examined the wavelength characteristics of the noise and compared the integrated noise during the reverse dc erase process with in situ remanent hysteresis curves. The integrated noise power followed the square of the first field derivative of the remanent hysteresis curve, (dM/dH)/sup 2/, showing that spatial fluctuation of the recording field inside the medium is a major source of the tape medium noise. It excluded spatial fluctuation of the medium coercivity as a possible noise source by comparing results from recording heads with two very different gap lengths. A quantitative analysis of the medium noise spectra at different erase currents indicated that interfacial roughness at the magnetic coating backside in some dual-layer media is a major source of medium noise. The conclusion: The main mechanism of the medium noise in advanced tape media is the head medium spacing fluctuation due to surface roughness.

Exchange coupling and switching fields of RE—TM double and triple layer stacks for direct overwrite

The recording properties of common single layer magneto-optical (MO) disks can be improved by introducing exchange coupled rare-earth (RE) transition-metal (TM) films, both from the point of view of capacity and data transfer rate. Direct overwrite (DOW) is a method to double the data transfer rate during writing, because the write process of new bits and the erase process of old bits is performed simultaneously. MO multilayer stacks must exhibit exchange coupling in order to be suitable for DOW. The switching fields of each layer depend on coercive energy, magnetic field energy and the energy of the interface wall between coupled layers. In this paper we discuss the dependence of switching fields on layer thickness and wall energy σw for several double and triple layer stacks. The memory and reference layers are TbFeCo and DyFeCo, respectively. Triple layer stacks have an intermediate layer (GdFe and GdFeCo) to adjust the wall energy. DOW presupposes a weak coupling at 300 K and a strong coupling at higher temperatures. This requires a very thick reference layer in double layer stacks, causing excessive heat capacities. However, for triple layers the DOW demands are met in much thinner stacks as the wall energy is adjusted through the intermediate layer. The wall energy of the intermediate layer is determined by its anisotropy. We studied the anisotropy of evaporated GdFe, GdCo and GdFeCo films as a function of composition. GdCo showed only in-plane anisotropy, while GdFe was perpendicularly magnetized for Fe contents up to 87 at%. Adding Co to GdFe leads to a layer with a temperature dependent easy axis. The carrier-to-noise ratio (CNR) of a series of magneto-optical disks, both double and triple layer stacks, was determined. The maximum CNR of 51.4 dB is comparable to results on a single layer disk with the same memory layer. On triple layer stacks a CNR > 45 dB could be written at a laser power below 9 mW.

Magnetic remanences of gyromagnetic origin in an iron-terbium thin film

The application of an alternating magnetic field at room temperature to a thin film of Tb/sub 0.17/Fe/sub 0.83/ is shown to produce a remanence of gyromagnetic origin (gyroremanent magnetization-GRM). This is the first time that such an effect has been observed in thin films. The GRM produced appears to have similar characteristics to that acquired by fine particles of single-domain size. A study of GRM in films may help to understand the dynamics of the magnetization response where gyromagnetic effects are important. GRM is the only remanence which, if measured as a function of temperature, is capable of detecting an angular momentum compensation temperature and thus may be of use, for instance, in trying to understand the erase process in single layer direct overwrite magneto-optical recording media since Weng and Kryder have recently proposed that this process may be a consequence of very high wall mobility at the angular momentum compensation temperature.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Measurement of Domain Wall Mobility in Magneto-Optic Media

Domain wall mobility in magneto-optic (MO) media is important in determining the thermomagnetic recording and erase process. However, measurement of domain wall mobility has been difficult due to the large coercivity of MO media near room temperature and the weak MO signal at high temperature. With an improved high speed polar Kerr MO camera system, the dynamics of domain wall motion can now be imaged and measured at temperatures near Tcurie. The domain wall mobility in GdTbFe samples was measured with the bubble collapse method. The experimental results show that the domain wall motion velocity is a linear function of applied bias field and the domain wall mobility is about 0.3 cm/sOe. Samples with different preparation methods are compared and the experiment shows that whereas the dynamic coercivity varies with the preparation method, the mobility is an intrinsic property and dependent primarily upon sample composition.

Erase Process and Tolerance Study of Pulse Erasure in a High-Density Magneto-Optical Disk Drive

The pulse erasure process in a TbFeCo magneto-optical medium is investigated. The effects of erase power, linear velocity, and erase/write delay on the pulse erasure residue are reported.

A new model of the erase process in single layer direct overwrite magneto-optical recording media

The effects of angular momentum compensation on domain wall motion are considered. Particular attention is paid to the dynamic parameters of the wall in response to effects brought about by the approach to the angular momentum compensation temperature. When the wall gets close to the angular momentum compensation point, the net angular momentum is effectively lowered, thus causing the mobility of the wall to increase markedly. This unusual behavior is believed to be responsible for the erase process in single-layer direct-overwrite magnetooptical recording media.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Mechanism of reverse dc erase noise in thin film media

The mechanism of reverse dc erase noise in thin film media was investigated by comparing integrated magnetization fluctuations in a reverse dc erase process with in situ measured remanence curves. In order to avoid the demagnetization effect in the write process and the head field fluctuations in the reverse dc noise measurement, a large-scale head was used as the source of the reverse dc fields. It was found that the integrated magnetization fluctuations as a function of the reverse field follow the first field derivative of the remanent curve, d M/d H, instead of (d M/d H) 2. It is concluded that reverse dc erase noise in thin film media originates from intrinsic magnetization fluctuations, which are strongly influenced by magnetic interactions between grains.