Probe Storage Research Articles

Efficient Light Probes for Real-Time Global Illumination

Reproducing physically-based global illumination (GI) effects has been a long-standing demand for many real-time graphical applications. In pursuit of this goal, many recent engines resort to some form of light probes baked in a precomputation stage. Unfortunately, the GI effects stemming from the precomputed probes are rather limited due to the constraints in the probe storage, representation or query. In this paper, we propose a new method for probe-based GI rendering which can generate a wide range of GI effects, including glossy reflection with multiple bounces, in complex scenes. The key contributions behind our work include a gradient-based search algorithm and a neural image reconstruction method. The search algorithm is designed to reproject the probes' contents to any query viewpoint, without introducing parallax errors, and converges fast to the optimal solution. The neural image reconstruction method, based on a dedicated neural network and several G-buffers, tries to recover high-quality images from low-quality inputs due to limited resolution or (potential) low sampling rate of the probes. This neural method makes the generation of light probes efficient. Moreover, a temporal reprojection strategy and a temporal loss are employed to improve temporal stability for animation sequences. The whole pipeline runs in realtime (>30 frames per second) even for high-resolution (1920×1080) outputs, thanks to the fast convergence rate of the gradient-based search algorithm and a light-weight design of the neural network. Extensive experiments on multiple complex scenes have been conducted to show the superiority of our method over the state-of-the-arts.

Design of bifunctional phase-change device for storage memories and reconfigurable metasurfaces

Herein, we design an optoelectronic device using phase-change materials (PCMs) and assess its ability to possess two functionalities: the perfect absorption of photonic metasurfaces and the high-density storage capability of electronic memories. Both functionalities are evaluated experimentally and via simulations. Such bifunctionalities are achieved according to the phase-transformation extent of the designed hybrid that comprises a phase-change stack having Si/SiO2/Au/Ge2Sb2Te5 (GST)/indium tin oxide (ITO) and a conductive PtSi probe. The use of PCM layers either in a full crystalline or an amorphous phase causes perfect absorption. The resonant wavelength of the device can be dynamically changed by modulating the phase-change extent of the PCM layer. Generating a continuous crystalline region or separated crystalline bits inside the amorphous GST exhibits a larger tuneability of the phase-change extent than forming separated amorphous bits inside the crystalline GST, and allows for a wider bandwidth of 300 nm for perfect absorber applications. Forming amorphous bit array inside crystalline background yields discernible optical reading contrast when compared to forming a crystalline bit array. The amorphous bit array configuration has an areal density of ～500 Gbits/inch2, data rate of 5 Mbits/s, and energy consumption of 92 pJ/bit. These values render the configuration attractive for probe storage applications. Such a designed hybrid with the ability to process data photonically and store data electronically exhibit its promising for highly integrated metasurface and superb compact electro-optical computing device.

Establishment of a 3D ultrasound imaging system based on pulse-triggered image acquisition

To establish a 3D ultrasound imaging system based on pulse-triggered image acquisition using the linear probe on the VerasonicsTM vantage 128 platform and evaluate its performance in scanning standard phantom and human carotid artery. The 3D ultrasound imaging system included 3 modules for probe motion control, image acquisition and storage, and 3D image reconstruction and display. To improve the precision of image acquisition, we used fixed frequency pulses to control the external trigger function combined with mechanical scanning. Voxel-based 3D reconstruction was used for image reconstruction and display. The user interface was designed to allow direct operations of the platform. We carried out scanning tests of standard ultrasound phantom and human carotid artery to evaluate the performance of this imaging system. We successfully constructed a 3D ultrasound imaging system based on pulse-triggered image acquisition. The results of standard phantom and human carotid scanning tests showed that each module of the system was fully functional. The self-designed user interface of this ultrasound imaging system allowed full control of the system functions for original image acquisition, 3D image reconstruction, and display of cross-sections in 3 different views. This 3D ultrasound imaging system achieves high-quality 3D ultrasound imaging and provides the basis for further study and clinical application of 3D ultrasound imaging.

Wettability Engineering for Studying Ion Transport in 2D Layered Materials

AbstractLayered materials are widely used for their capacity to incorporate and store foreign ionic species. It has become possible to exploit this process at the level of single crystals consisting of individual atomic layers: 2D materials and their van der Waals heterostructures. Due to the small size of available high‐quality specimen, however, it remains challenging to probe ion transport and storage in these systems. To promote future advances in this field, wettability engineering is introduced as a strategy for the on‐chip integration of electrolytes with micrometer‐sized samples of 2D materials. Contact angles are systematically measured for a variety of electrolyte–surface couples to identify a rational device design, and engineer lateral contrasts in surface chemistry to control the rims of drop cast electrolytes with micrometer precision. This allows covering single crystalline flakes of 2D materials only partially, leaving most of the sample surface uncovered and imposing directionality on ion transport. Wettability engineering is used to fabricate few‐layer graphene electrochemical micro two‐compartment cells that display chemical diffusion of lithium on the order of 10−8 cm2 s−1. While the approach is transferrable to other 2D materials and ionic species, it can also benefit device design for the study of nonlocal electrolyte gating effects.

Recent Progress on Probe-Based Storage Devices

Prosperity of information technology triggers a tremendous amount of digital data that needs to be stored by storage memories with ultra-high capacity. Although probe-based memory has exhibited its superb storage merits, its developments to date, however, remain slow due to several physical limits. In order to overcome its drawbacks, and to further advance probe storage technologies, a comprehensive review regarding the current status and future prospect of probe-based memories become of importance. In this paper, we first presented the physical principles of various reported probe-based memories and their respective advantages/disadvantages, as well as their current status. Subsequently, up-to-date progress made on these probe memories and some novel probe memories concepts is proposed. The prospect of a probe-based memory device is finally predicted.

Temporal optical memory based on coherent population and two-photon coherence oscillations

We consider the ${F}_{g}=1\ensuremath{\rightarrow}{F}_{e}=1$ transition between the ground and excited hyperfine levels in alkali-metal vapor interacting with $\ensuremath{\sigma}$ linearly polarized control and probe fields whose polarizations can be either parallel or perpendicular to each other. We develop a matrix formulation that allows a solution of the Bloch equations to all orders in the pump and probe Rabi frequencies. Using this formalism, we calculate the steady-state probe absorption spectrum, the coherent population oscillations (CPOs), and two-photon coherence, in the absence (degenerate case) and presence (nondegenerate case) of a longitudinal magnetic field. We then calculate the probe storage when the pump is switched off and on again. We are particularly interested in whether the probe regains its original temporal shape when the pump is switched on again for the case of identical pump and probe frequencies. We show that, in the nondegenerate case, the restored probe does not regain its original shape whereas, in the degenerate case, the original shape is restored. This can be explained by considering the relative magnitudes of the CPOs which do not remember the temporal shape of the probe and the two-photon coherence oscillations which store the probe shape when the pump is switched off, as in electromagnetically induced transparency memories. In the nondegenerate case, the CPOs are much stronger than the two-photon coherence oscillations whereas, in the degenerate case, they are of similar magnitudes. Thus it is the two-photon coherence oscillations that are responsible for the restoration of the temporal shape of the probe in the degenerate case.

Ultrahigh Storage Densities via the Scaling of Patterned Probe Phase-Change Memories

The scaling potential of patterned probe phase-change memory (PP-PCM) cells is investigated, down to single-nanometer dimensions, using physically realistic simulations that combine electrothermal modeling with a Gillespie Cellular Automata (GCA) phase-change model. For this study, a trilayer TiN/Ge2Sb2 Te5/TiN cell structure (isolated by an SiO2 insulator) was preferred, due to its good performance and practicability, over previously investigated probe-based structures such as those that used diamond-like carbon capping layers or immersion in an inert liquid to protect the phase-change layer (while still allowing for electrical contact). We found that PP-PCM cells with dimensions as small as 5 nm could be successfully amorphized and recrystallized (RESET and SET) using moderate voltage pulses. The resistance window between the RESET/SET states decreased with a reduction in cell dimensions, but it was still more than the order of magnitude even for the smallest cells, predicting that PP-PCM cells are indeed scalable and operable in the sub10-nm region. Most importantly, it was found that the storage density could be increased by cell size scaling with storage densities as high as 10 Tb/in2 being achieved, which is significantly higher than the storage densities previously reported in the phase-change probe storage, and other probe-based technologies such as thermomechanical, magnetic, and ferroelectric probe storage.

Electrical resistivity optimization of diamond-like carbon thin film for electrical probe storage application

Abstract Today, the total amount of global data has been increasing at a phenomenal rate, and this necessitates the requirement for significant improvement in the storage capacity of current storage devices. Compared with other conventional storage devices, electrical probe memory exhibits several storage superiorities and is considered as the candidate for the next-generation mainstreaming storage device. In this case, to further mitigate the performances of the electrical probe memory, its architecture was previously optimized by simulation while lacking adequate experimental support. Therefore, we measured the electrical resistivities of the diamond-like carbon (DLC) capping and bottom layers by varying the film thickness, sputter power, and sputter pressure to thus establish the physically realistic property values of the DLC film. According to experiments, a 10 nm DLC capping layer with a resistivity of 0.1 Ω·m, and a 30 nm DLC bottom layer with a resistivity of 0.01 Ω·m, which most closely matches the theoretical prediction, are introduced into the originally designed electrical probe memory, and the subsequent recording experiment demonstrated the ability to achieve ultra-high density, large data rate, and ultra-low energy consumption using the redesigned architecture.

Overview of Probe-based Storage Technologies.

The current world is in the age of big data where the total amount of global digital data is growing up at an incredible rate. This indeed necessitates a drastic enhancement on the capacity of conventional data storage devices that are, however, suffering from their respective physical drawbacks. Under this circumstance, it is essential to aggressively explore and develop alternative promising mass storage devices, leading to the presence of probe-based storage devices. In this paper, the physical principles and the current status of several different probe storage devices, including thermo-mechanical probe memory, magnetic probe memory, ferroelectric probe memory, and phase-change probe memory, are reviewed in details, as well as their respective merits and weakness. This paper provides an overview of the emerging probe memories potentially for next generation storage device so as to motivate the exploration of more innovative technologies to push forward the development of the probe storage devices.

Compact and low power ADCs for a MEMS-based probe storage device

In this paper, we investigate the most appropriate ADC for an array of probe storage devices. Power consumption and area are crucial in this application, since one ADC is associated with each read channel. The read-channel specifications of the probe storage device require an ADC with seven bits of resolution at a rate of 100 kSample/s. Five different ADC architectures have been implemented for the desired specifications: a first- and a second order discrete-time $$\Sigma\Delta,$$ Σ Δ , a second order continuous-time $$\Sigma\Delta$$ Σ Δ and a cyclic ADC. The system and circuit design methods of each architecture are presented. The different architectures are compared based on the measurement results of the five fabricated circuits.

Information storage and retrieval for probe storage using optical diffraction patterns

A method for fast information retrieval from a probe storage device is considered. It is shown that information can be stored and retrieved using the optical diffraction patterns obtained by the illumination of a large array of cantilevers by a monochromatic light source. In thermo-mechanical probe storage, the information is stored as a sequence of indentations on the polymer medium. To retrieve the information, the array of probes is actuated by applying a bending force to the cantilevers. Probes positioned over indentations experience deflection by the depth of the indentation, probes over the flat media remain un-deflected. Thus the array of actuated probes can be viewed as an irregular optical grating, which creates a data-dependent diffraction pattern when illuminated by laser light. We develop a low complexity modulation scheme, which allows the extraction of information stored in the pattern of indentations on the media from Fourier coefficients of the intensity of the diffraction pattern. We then derive a low-complexity maximum-likelihood sequence detection algorithm for retrieving the user information from the Fourier coefficients. The derivation of both the modulation and the detection schemes is based on the Fraunhofer formula for data-dependent diffraction patterns. The applicability of Fraunhofer diffraction theory to the optical set-up relevant for probe storage is established both theoretically and experimentally. We confirm the potential of the optical readout technique by demonstrating that the impairment characteristics of probe storage channels (channel noise, global positioning errors, small indentation depth) do not lead to an unacceptable increase in data recovery error rates. We also show that for as long as the Fresnel number F ≤ 0.1, the optimal channel detector derived from Fraunhofer diffraction theory does not suffer any significant performance degradation.

Scanning probe memories – Technology and applications

Scanning probe-based memories have demonstrated their ability to store data at ultra-high densities, well in excess of 1 Tbit/sq.in. In addition they offer the capability for relatively fast writing and reading, in excess of 1 Mbit/second/tip, combined with very low energy consumption (a few pico Joules of writing energy per bit). Thus, scanning probe-based technology would seem to offer an attractive route for the provision of ultra-compact, ultra-high density, ultra-low power memories. In this paper we discuss the three major families of probe storage: (i) probe storage using thermo-mechanical (and purely mechanical) write/read in polymer media; (ii) probe storage using electrical writing (and various readout methods) in ferroelectric media; (iii) probe storage using electro-thermal writing and electrical reading in phase-change media. We discuss the physical principles behind the writing and reading methods in each case, as well as media and (probe) tip design and fabrication issues. We also review very briefly some of the potential application areas for probe storage.

Channel Modeling and Detector Design for Dynamic Mode High Density Probe Storage and Nano-imaging Applications

AbstractIn this paper, we provide a consolidated summary of the work reported in [1], [2], [3], [4] which is based on probe based high density storage and nano-imaging using atomic force microscopy (AFM) setup. In probe based high density storage, we consider a data storage system that operates by encoding information as topographic profiles on a polymer medium. A cantilever probe with a sharp tip (few nm radius) is used to create and sense the presence of topographic profiles, resulting in a density of few Tb per in.2. The high quality factor dynamic mode operation, that is less harsh on the media and the probe, is analyzed. The read operation is modeled as a communication channel which incorporates system memory due to inter-symbol interference and the cantilever state. Next, the solutions to the maximum likelihood sequence detection problem and maximum a posterior (MAP) symbol detection problem based on the Viterbi algorithm and BCJR algorithm respectively are devised. Experimental results demonstrate that the performance of the Viterbi and BCJR detectors are several orders of magnitude better than the performance of other existing schemes.Nano-imaging has played a vital role in basic sciences as it enables interrogation of material with sub-nanometer resolution. In this paper, we also present a high speed one-bit imaging technique using dynamic mode AFM with a high quality factor cantilever. Experimental results demonstrate that our proposed algorithm provides significantly better image resolution compared to current nano-imaging techniques at high scanning speed.

Write strategies for multiterabit per square inch scanned-probe phase-change memories

A mark-length write strategy for multiterabit per square inch scanned-probe memories is described that promises to increase the achievable user density by at least 50%, and potentially up to 100% or more, over conventional approaches. The viability of the write strategy has been demonstrated by experimental scanning probe write/read measurements on phase-change (GeSbTe) media. The advantages offered by adopting mark-length recording are likely to be equally applicable to other forms of scanned probe storage.

Maximum-likelihood sequence detector for dynamic mode high density probe storage

There is an increasing need for high density data storage devices driven by the increased demand of consumer electronics. In this work, we consider a data storage system that operates by encoding information as topographic profiles on a polymer medium. A cantilever probe with a sharp tip (few nm radius) is used to create and sense the presence of topographic profiles, resulting in a density of few Tb per in. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The prevalent mode of using the cantilever probe is the static mode that is harsh on the probe and the media. In this article, the high quality factor dynamic mode operation, that is less harsh on the media and the probe, is analyzed. The read operation is modeled as a communication channel which incorporates system memory due to inter-symbol interference and the cantilever state. We demonstrate an appropriate level of abstraction of this complex nanoscale system that obviates the need for an involved physical model. Next, a solution to the maximum likelihood sequence detection problem based on the Viterbi algorithm is devised. Experimental and simulation results demonstrate that the performance of this detector is several orders of magnitude better than the performance of other existing schemes.

Channel Modeling and Signal Processing for Probe Storage Channels

Probe-storage devices employ large arrays of probes to write/read data in parallel in some storage medium, and combine ultra-high density, low access times, and low power consumption. A particular probe-storage technique utilizes thermomechanical means to store and retrieve information in thin polymer films. In this paper, a system-level channel model for the thermomechanical probe-storage channel is presented. Each of the components of the proposed model is derived by extensive characterization of experimentally obtained readback signals from probe recording tests. Moreover, detection techniques that are actually utilized in a probe-storage prototype implementation are described, followed by coding techniques for added reliability in the presence of particles or other impurities of the storage medium. In addition to low-complexity coding constructs, a concatenated coding scheme with an outer LDPC and inner modulation code is considered, in order to establish a benchmark for overall system performance. A novel methodology for joint decoding of outer LDPC and inner (d,k) modulation codes is developed. Furthermore, an optimal soft decoder for the modulation code is proposed, based on a modification of the decoder metrics to accurately account for the probe storage channel output statistics. Experimental results are used throughout the paper to validate the channel model and identify its relevant parameters, as well as to verify the system performance obtained by simulations.

The construction of Si2Sb2Te5 electrical probe storage based on UV nanoimprint lithography

The Si2Sb2Te5 (SST) storagearray with a density of 2.4 Gbit inch−2 was fabricated by UV nanoimprint lithography (UV-NIL) and filling semiconductortechnology. The area of the SST storage cell contacted with electrodes was0.031 µm2. Structural transformation of SST during heating was in situ studied by time-resolved x-raydiffraction (XRD). An electrical probe storage system was constructed by SST combiningwith a conductive atomic force microscope (C-AFM) with a nanoprobe. Switching of theSST electrical probe storage cell from the high resistance state to the low resistancestate had been achieved, and the rate of these two resistance states was 37.71.The current increased apparently when the applied voltage exceeded 1.79 V.

Nano-positioning of an electromagnetic scanner with a MEMS capacitive sensor

This paper presents the control design and experimentation of a prototype electromagnetic X/Y scanner for small form factor probe storage. An array of probe heads is to be precisely positioned in tracking, scanning and rotation directions so that high areal density (>1 terabit/in 2) and high data throughput can be achieved. The scanner has X/Y motion capabilities with a linear stroke of about 300 μ m . It can also generate rotational motion with offset actuators to compensate for disturbances, mechanical tolerance and nonlinearities. System characterization, modeling, MIMO control design and simulation, and preliminary experimental results are presented. The feasibility of rotation control with the capacitive sensor and offset actuators is experimentally confirmed.

Fabrication, constructions and electrical property of Si2Sb2Te5 electrical probe storage system

A Si2Sb2Te5 (SST) memory array with density of 4 Gbit/in.2 was fabricated by ultraviolet-imprint lithography. The contacted area of SST with electrodes in memory cell was 0.0392 μm2. Crystal structure transformation of SST film was studied. Adhesion strength of sample interface was tested by Nano Indenter®. Electrical property of SST electrical probe storage (EPS) system was measured. Resistance of as-deposited SST film was about four orders of magnitude higher than that of the one annealed at 350°C. Resistance of EPS cell dropped about two orders from high-resistance state to low-resistance state.

Nanoprecision MEMS Capacitive Sensor for Linear and Rotational Positioning

This paper presents a microelectromechanical systems (MEMS) capacitive position sensor for nanopositioning applications in Probe storage systems. The objective of the sensor system design is to develop a high-precision <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> - <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Y</i> linear and rotational position sensor with a minimum sensor area and a large range of movements at high speed. To achieve this, first, a simple sensor noise model scalable with a sensor area was developed, in which all the parasitic capacitances are taken into account. Furthermore, a signal-processing solution was developed to compensate for the nonlinearities caused by rotational disturbances and, at the same time, to generate a rotational position signal for active rotation-control purposes. A MEMS capacitive sensor prototype was constructed with the design of a 13-mum pitch, a 300-mum peak-to-peak linear stroke, and a 3.46-mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> sensor area at a 3-mum gap. The measured sensor noise was 0.2 nm 1sigma, which corresponds to 12 mudeg 1sigma for the fabricated prototype sensor, at 25-kHz bandwidth. Furthermore, the signal linearity was significantly enhanced by the proposed sensor signal processing, with a measured sensor signal nonlinearity of 0.78% for an 80-mum peak-to-peak stroke at 200 Hz. Finally, the capacitive sensor-based dynamic closed-loop <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> - <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Y</i> linear and rotational position control of an electromagnetic scanner was successfully demonstrated.