Non-destructive Read Research Articles

Operation of Ferroelectric Gate Field-Effect Transistor Memory with Intermediate Electrode using Polycrystalline Capacitor and Metal–Oxide–Semiconductor Field-Effect Transistor

We have investigated the basic operation of a ferroelectric gate field-effect transistor (F-FET) memory with an intermediate electrode for data writing, using a discrete circuit which consists of a polycrystalline ferroelectric capacitor connected serially to the gate of a commercial n-channel metal–oxide–semiconductor (MOSFET). By sputtering, a ferroelectric capacitor Cf was formed as a (RuO2 top electrode)/poly-Pb(Zr0.52Ti0.48)O3(PZT)/(Pt/RuO2 bottom electrode) structure on a SiO2/Si substrate. The readout characteristics showed nondestructive operation. It was also shown that the output voltage for the positive and the negative polarization memory states corresponded very well with the intermediate electrode voltages on the gate of the MOSFET. Furthermore, the ratio of the ferroelectric capacitor to the input capacitor of the MOSFET was found to be an important factor influencing the cycle number of nondestructive reading and the difference in output voltage between the positive and negative polarization states.

A DUAL-GATE CELL (DGC) FeRAM WITH NDRO AND RANDOM ACCESS SCHEME FOR NANOSCALE AND TERABIT NON-VOLATILE MEMORY

ABSTRACT This paper proposes a new dual-gate cell (DGC) FeRAM. The dual-gate cell is composed with MFSFET and MOSFET faced in parallel with common drain, source and float channel. The gates of the dual-gate cell are controlled by wordline and bottom wordline, respectively. A multitude of the dual-gate cells are arrayed in serial connection for unit array scheme. The WL_1 to WL_m of MFSFET are not biased for sensing operation in read mode, thus there are no degradation and disturbance to the cell retention data in read access. The write cycle composed with two sub-write cycles of data ‘1’ preserve or data ‘0’ write cycle after the first sub-write cycle of data ‘1’ write to all active cells. The data ‘1’ is preserved by the same voltage polarity between WL_1 and channel voltage of the MFSFET. The random access operation is possible in both read and write mode with non-destructive read out (NDRO).

Fault tolerant function of dynamic refreshing holographic memory with shutter-less optical feedback circuit

The optical system, consisting of two photorefractive memories and a shutter-less optical feedback circuit, will be demonstrated to function as data mirroring. This function is known to automatically detect the data dropout and restore data, using unimpaired data in another memory, in the event that part or all of the data in either of them were lost for some reason. This memory system also can cope with a damaged hologram, a result of reading beams, which is a disadvantage of rewritable photorefractive memory, to ensure non-destructive holographic reading. It can be achieved by using no electronic circuits or mechanical structures; our optical experimental method in particular obtains this basic action.

A Ferroelectric Associative Memory Technology Employing Heterogate FGMOS Structure

A ferroelectric associative memory technology has been developed using ferroelectric materials as a means of storing template vector information. In order to accommodate the ferroelectric memory cell to associative processing circuits, a heterogate floating-gate MOS structure has been developed. As a result, nondestructive reading of analog data written in the ferroelectric film has been made possible, allowing a wide voltage range of input signals to associative processing circuits. The concept has been experimentally verified using fabricated test devices and circuits.

A Novel Ferroelectric FET Based Memory Cell of Minimum Size and Non-Destructive Reading

We propose a single device, which can perform the function of a ferroelectric inverter and be used as a basic cell of ferroelectric random access memory (FRAM) with non-destructive read out (NDRO). This device has a minimized geometry suitable for high density integration. The write voltage required is the same lowest possible level for “0” and “1” states. Consequently, such a device as a FRAM cell can be operated at low voltages for both READ and WRITE operations with minimum power consumption. A preliminary testing device was fabricated using conventional dielectrics in place of ferroelectrics, and it worked as expected.

NanoCell electronic memories.

NanoCells are disordered arrays of metallic islands that are interlinked with molecules between micrometer-sized metallic input/output leads. In the past, simulations had been conducted showing that the NanoCells may function as both memory and logic devices that are programmable postfabrication. Reported here is the first assembly of a NanoCell with disordered arrays of molecules and Au islands. The assembled NanoCells exhibit reproducible switching behavior and two types of memory effects at room temperature. The switch-type memory is characteristic of a destructive read, while the conductivity-type memory features a nondestructive read. Both types of memory effects are stable for more than a week at room temperature, and bit level ratios (0:1) of the conductivity-type memory have been observed to be as high as 10(4):1 and reaching 10(6):1 upon ozone treatment, which likely destroys extraneous leakage pathways. Both molecular electronic and nanofilamentary metal switching mechanisms have been considered, though the evidence points more strongly toward the latter. The approach here demonstrates the efficacy of a disordered nanoscale array for high-yielding switching and memory while mitigating the arduous task of nanoscale patterning.

CuPc/PbZr 0.2Ti 0.8O 3/(La,Ba)MnO 3 field effect transistor heterojunction photomemory

We investigated a photoconductor(PC)/ferroelectric oxide(OF)/semiconductor oxide(SO) POS-FET structure photomemory consisting of organic photoconductor CuPc/inorganic ferroelectric PbZr 0.2Ti 0.8O 3 heterojunction gate and a ferromagnetic oxide semiconductor La 0.87Ba 0.13MnO 3 channel. Visible light information detected by photoconductor CuPc can be memorized in ferroelectric PbZr 0.2Ti 0.8O 3, and non-volatile and non-destructive reading out process of light information memorized in this ferroelectric layer were achieved by reading out the resistance modulation of ferromagnetic semiconductor oxide La 0.87Ba 0.13MnO 3 channel under the photoconductor/ferroelectric gate.

Organic bistable molecular memory using photochromic diarylethene

A principle of organic memory device using a bistable photochromic molecule is presented that allows extremely high bit densities and very low power consumption. This device is based on an isomerization reaction of photochromic diarylethene molecule via its excited state by an electric carrier injection, not by photon absorption. Experimental data show that the reversible writing and nondestructive reading of information by the carrier injection is feasible. The advantages and properties of such an organic semiconductor memory using a bistable molecule are discussed.

Photo-optical behaviour of a photosensitive chiral nematic copolymer and mixtures containing non-chiral photoactive azobenzene groups

For the first time, the phenomenon of the light-induced increase in helix pitch length is described for cholesteric polymer systems containing photosensitive non-chiral fragments. This phenomenon is observed for a copolymer and mixtures containing azobenzene fragments which are able to undergo E-Z photoisomerization. In all cases, upon UV irradiation, the selective light reflection maximum is shifted to the long wavelength spectral region. This shift appears to be quite appreciable and, in some cases for mixtures, it might be as high as 300 nm. This process is known to be thermally reversible: upon annealing, the selective light reflection maximum comes back to its initial position. The specific features of the kinetics of this photoprocess were studied, and the fatigue resistance of such systems investigated. The advantages of their application for reversible recording of optical information with a possible non-destructive data reading is outlined.

An RSFQ variable duty cycle oscillator for driving a superconductive qubit

We design an RSFQ oscillator with a variable duty cycle to drive a superconductive qubit. This design has been optimized to minimize the decoherence when coupled to the superconductive persistent current qubit. A continuous RSFQ ring oscillator reads the contents of a Non-Destructive Read Out memory cell. By using two out-of-phase counters to Set and Reset the cell, we can vary the duty cycle of the pulses read from the memory cell. This train of flux quanta is filtered, then used to drive the persistent current qubit. The precision is sufficient to measure relaxation time and possibly Rabi oscillations.

A ferroelectric memory-based secure dynamically programmable gate array

A nonvolatile ferroelectric memory-based eight-context dynamically programmable gate array (DPGA) enables low-cost field programmable systems by the elimination of off-chip nonvolatile memories as well as the multicontext architecture. Since read and program sequences of configuration data loading from/to the DPGA are securely protected, unauthorized users cannot access the stored configuration data. The associated configuration memory consists of a SRAM-based six-transistor and 4-ferroelectric capacitor cell. The developed configuration memory achieves access time of 4ns, comparable to standard SRAM, which is 20 times faster than conventional ferroelectric memory; furthermore, it features a nondestructive read operation and a stable data recall scheme. The employed logic block circuit can effectively improve the available number of logic gates for the multicontext scheme with minimum area overhead. The prototype nonvolatile DPGA is fabricated in a 0.35-/spl mu/m CMOS with ferroelectric memory technology, and the implementation result of the Data Encryption Standard (DES) encryption/decryption functions on this DPGA presents proper operation up to 51 MHz at 3.3V. The nonvolatile storage of configuration memory is verified for power-supply voltage as low as 1.5 V at room temperature, which is the lowest operation voltage ever reported for PbZrTiO/sub 3/ (PZT)-based ferroelectric memories.

Growth and Characteristics of SrBiNbO Thin Films for Memory Devices

thin films were grown on Pt/Ti/Si and p-type Si(100) substrates by rf-magnetron co-sputtering method using two ceramic targets, . The structural and electrical characteristics have been investigated to confirm the possibility of the SBN thin films for the applications to destructive and nondestructive read out ferroelectric random access memory(FRAM). For the optimum growth condition X-ray diffraction patterns showed that SBN films had well crystallized Bi-layered perovskite structure after heat-treatment in furnace. From this specimen we got remnant polarization of about 6 uC/ and coercive voltage of about 1.5 V at an applied voltage of 5 V. The leakage current density was /A/ at an applied voltage of 5V. And for the NDRO-FRAM application, properties of SBN films on Si substrate has been investigated. From transmission electron microscopy (TEM) analysis, we found the furnace treated sample had a native oxide about 2 times thicker than the RTA treated sample and this thick native oxide layer had a bad effect on C-V characteristics of SBN/Si thin film. After RTA process, we got the improved memory window of 1.3 V at an applied voltage of 5 V.

The development of a micro-Faraday array for ion detection

A micro-Faraday array detector was evaluated for use as an ion detector for mass spectrometry. This charge-integrating detector was based upon the merging of technologies from the fields of CCDs and infrared (IR) multiplexers. Measurements were performed by exposing the detector to an Ar + ion beam of low flux. The array detector responds to both positive and negative charges and preliminary results indicate a detection limit of 100 ions. Current data indicate that the linear dynamic range of the device is over five orders of magnitude. The capability of the device to perform specialized charge read out modes could theoretically both lower the detection limit by a factor of seven and increase the linear dynamic range to nine orders of magnitude using non-destructive read outs.

The performance of AI/PZT/ZrO2/Si FET structure

Metal/Ferroelectric/Insulator/Semiconductor (MFIS) field effect transistor was researched by using Si (100) as substrate, ZrO2 as insulator layer, Sol-Gel grown PZT film as ferroelectric material, Al as metal layer. The annealing conditions of ZrO2 and PZT were 800°C and 675°C, in O2 atmosphere, respectively. The thickness of PZT and ZrO2 were chosen as 240nm and 20 nm in this MFIS structure. The C-V characteristics of MFIS structure has been studied. Under the testing voltage±5V and frequency 1MHz, the maximum memory window reached 3V. The IDS-VDS characteristics of MFIS FET has also obtained for W/L=500 μ m/50 μ m and 40 μ m /8 μ m structures. Correct reading & writing functions of non-volatile memory and nondestructive read out have been realized by such a MFIS FET under the condition of VDS = ±10V.

Optical information storage of bacteriorhodopsin molecule film: experimental study

We present here an experiment of optical information storage of bacteriorhodopsin (BR) polymer film made from variant M1B. A recording system of three-wavelength has been set up in the experiment. The photoexcited P(490) state shows a permanent storage property confirmed by our contrast ratio experiments. It is found out that the readout contrast ratio is very sensitive to the intensity and wavelength of probe beam and the recorded data can be readout from 530–630 nm with different contrast ratio. Within the range 570–600 nm, a better contrast ratio can be obtained. Considering the erasing effect for the reason of absorption of P state, by using 594 nm as the readout wavelength both higher contrast ratio and nondestructive reading can be realized.

SBT-based ferroelectric FET for nonvolatile non-destructive read out (NDRO) memory applications

SrBi2Ta2O9 based Ferroelectric FETs with a CeO2 buffer layer deposited by Metal Organic Decomposition (MOD) were fabricated on p-Si (100) substrate and analyzed in detail. The hysterisis curve (drain current vs. gate voltage) of the FET shows the counter-clockwise direction, which demonstrates the change of channel conductivity due to the ferroelectric polarization. The memory window with the gate voltage of ±10V was 2V. The difference of current ratio of Ids(on) to Ids(off) was 5∼7 orders in magnitude which is easily sensed by sense amplifiers. The charges of “on” state stored decay logarithmically with time without severe initial loss of data. This indicates the FET-FeRAM can be implemented in NDRO applications.

Characteristics of Pt/SrTiO 3/Pb(Zr 0.52, Ti 0.48)O 3/SrTiO 3/Si ferroelectric gate oxide structure

Pt/SrTiO 3/Pb(Zr 0.52, Ti 0.48)O 3/SrTiO 3/Si (MIFIS) ferroelectric gate oxide structures were prepared by an r.f. sputtering method for application of non-destructive read out ferroelectric RAM (NDRO-FRAM) devices. In the MIFIS structure, a SrTiO 3 (STO) film was used as a buffer layer to prevent the interaction between the Pb(Zr 0.52,Ti 0.48)O 3 (PZT) film and the Si substrate and also between the PZT film and the Pt top electrode. In the PZT/Si structure, a serious inter-diffusion of Pb into Si substrate was observed by Auger electron spectrometry (AES). However, STO/PZT/STO/Si structures had a perfect perovskite phase and a flat interface of PZT/STO/Si without the inter-diffusion of Pb into the Si substrate. When Pt/STO/PZT/STO/Si structures were post-annealed at 400°C for 30 min after depositing the Pt top electrodes, the leakage current of MIFIS structure was improved to about 10 −8 A/cm 2. The property of the memory window of MIFIS structures was improved due to a low leakage current. When Pt/STO(25 nm)/PZT(160 nm)/STO(25 nm)/Si structures were annealed at 600°C for 1 h and post-annealed at 400°C for 30 min, the maximum value of the memory window was about 2 V at the applied voltage of 7 V. The memory window was increased as increasing the thickness of PZT film since a higher voltage was applied to the thicker PZT film.

Data reading with the aid of one-photon and two-photon luminescence in three-dimensional optical memory devices based on photochromic materials

The problem of nondestructive reading of the data stored in the interior of a photochromic sample was analysed. A comparison was made of the feasibility of reading based on one-photon and two-photon luminescence. A model was proposed for the processes of reading the data stored in photochromic molecules with the aid of one-photon and two-photon luminescence. In addition to photochromic transitions, account was taken of the transfer of populations between optically coupled transitions in molecules under the action of the exciting radiation. This model provided a satisfactory description of the kinetics of decay of the coloured form of bulk samples of spiropyran and made it possible to determine experimentally the quantum yield of the reverse photoreaction as well as the two-photon absorption cross section of the coloured form. Measurements were made of the characteristic erasure times of the data stored in a photochromic medium under one-photon and two-photon luminescence reading conditions. It was found that the use of two-photon luminescence made it possible to enhance considerably the contrast and localisation of the optical data reading scheme in three-dimensional optical memory devices. The experimental results were used to estimate the two-photon absorption cross section of the coloured form of a sample of indoline spiropyran in a polymethyl methacrylate matrix.

Transient photocurrents in lead zirconate titanate thin films

Transient photocurrents are investigated in ferroelectric lead zirconate titanate (PZT) films illuminated by laser pulses in the spectral range of 340–380 nm. At low electric fields, the photocurrent is sensitive to the ferroelectric polarization state and changes sign upon the polarization switching. At higher fields, the polarization-independent current proportional to the applied electric field is dominant. The spectral dependence of polarization-dependent current is controlled by the excitation of charge carriers over the forbidden band of PZT having a maximum near 3.5 eV. Possible mechanisms of the observed effect are discussed and the possibilities of a nondestructive read out of polarization state in the ultraviolet spectral range are demonstrated.

Nondestructive readout of a three-dimensional photochromic optical memory with a near-infrared differential phase-contrast microscope

A three-dimensional (3D) rewritable optical memory using photochromic material is described for high-density memory. The bits are recorded in a 3D volume of photochromic material. A transformation of the photochromic molecule between two isomers with different absorption spectra can be stimulated by irradiation with appropriate wavelengths. We show that a nondestructive readout of photochromic memory is possible by use of a small difference in the refractive index of the photochromic isomers in the near-IR range. For this purpose a near-IR laser-scan differential phase-contrast microscope is used. Experimental results of 3D recording and nondestructive reading are presented.