Scanning Nonlinear Dielectric Microscopy Research Articles

Three-dimensional observation of nanoscale ferroelectric domains using scanningnonlinear dielectric microscopy with electric field correction by Kelvin probe forcemicroscopy

An advanced technique for the measurement of three-dimensional ferroelectricdomain structure is described. Scanning nonlinear dielectric microscopy is usedto measure the polarization components both perpendicular and parallel to thespecimen surface. A nanoscale electric field correction is devised and performed usingKelvin probe force microscopy to allow more precise measurement of the nanoscalepolarization component parallel to the specimen surface. Using this electric fieldcorrection, three-dimensional imaging of the ferroelectric polarization orientation isdemonstrated.

High-Density Ferroelectric Recording Using Diamond Probe by Scanning Nonlinear Dielectric Microscopy

In this paper, we report the development of a diamond multiprobe for ultrahigh-density ferroelectric data storage based on scanning nonlinear dielectric microscopy (SNDM), which is a technique for determining polarized directions in ferroelectric domains by measuring a nonlinear dielectric constant with an electrical inductance–capacitance (LC) resonator. SNDM has the capability of both reading and writing nanosized polarized ferroelectric domain information at a high speed, since the SNDM technique is a purely electrical method. Boron-doped diamond synthesized by hot-filament chemical vapor deposition is chosen as a conductive and robust probe material. The diamond probes are fabricated using a combination of the silicon lost-mold technique and selective growth. We present the fabrication of the diamond multiprobe and data storage experiments using a ferroelectric LiTaO3 thin film. It is demonstrated that the boron-doped diamond probe can be used for data storage based on SNDM.

Nanodomain Manipulation for Reduction of Bit Error Rate in Terabit/Inch2-Class Ferroelectric Data Storage

Actual information data storage was studied using a data storage system based on scanning nonlinear dielectric microscopy. The bit error rates of the data recorded on a LiTaO3 single-crystal medium were evaluated. The data were written at the density of 403 Gbit/in.2 using a conductive-diamond-coated cantilever as a read/write probe. The tendencies of the bit errors were affected by the arrangement of the surrounding data bits. A writing method using bipolar pulses was discussed in order to decrease the bit error rate. The data with the highest recording density, 0.98 Tbit/in.2, were recorded by using a sharp cantilever. The bit error rate was decreased by a factor of four by adjusting the pulse amplitudes according to the bit arrangements.

Doping integrity diagnostics of planar transistor channel structures by scanning nonlinear dielectric microscopy

The integrity of doping in transistor structures was diagnosed using scanning nonlinear dielectric microscopy (SNDM). Nonlinear capacitance profiling and pinpoint capacitance-voltage analysis were done through SNDM, and the results clearly discriminated between a depletion layer and a tailing of carrier distribution due to outdiffusion of dopants in an n+∕p junction. This analysis was applied to n+∕p∕n+ and p+∕n∕p+ transistor channel structures formed with different process parameters. An increase in the n+ activation temperature from 800to950°C caused a narrowing of the p-type region in the n+∕p∕n+ structure. A decrease in the substrate doping concentration from 2×1018to2×1017cm−3 caused a depletion of the entire channel when the gate length was less than 200nm. The influence of channel depletion was proven to be more severe in p+∕n∕p+ transistor channel structures because boron had higher diffusivity than arsenic.

Cross-Sectional Observation of Nano-Domain Dots Formed in Congruent Single-Crystal LiTaO3

ABSTRACTCross-sectional shapes of reversal nano-domain dots formed in a congruent LiTaO3 single-crystal recording medium were studied by scanning nonlinear dielectric microscopy (SNDM). Images obtained by SNDM measurements confirm that reversal nano-domain dots penetrate through the entire sample. The domain wall thickness was evaluated by the cross-sectional measurement results. The variation of the domain wall thickness as a function of sample thickness and of depth position was evaluated. It was found that thinner samples have a tendency to have thinner domain walls, and it was confirmed that the domain wall thickness at the bottom of the sample was thinner than at the front surface of the sample. A discussion of the measured result is also provided.

How Humidity Affects on Scanning Nonlinear Dielectric Microscope

The dopant type and carrier concentration in a patterned semiconductor sample with three different doping regions were measured by scanning nonlinear dielectric microscope (SNDM). SNDM is used in the way of a scanning capacitance microscopy (SCM) with a new detection mechanism based on frequency detection. The topographic, pn-distribution and the carrier concentration images of a patterned semiconductor sample were measured at the same time. In concurrence with a demonstration of the SNDM-SCM measurements, the influence of an adsorbed water layer on measurements is evaluated in the vacuum and in the air over a relative humidity (RH) range of 20 to 80%. Adverse affects on capacitance measurements due to the variation in RH are revealed. [DOI: 10.1380/ejssnt.2006.454]

Simultaneous Observation of Surface Morphology and Dielectric Properties Using Non-Contact Scanning Nonlinear Dielectric Microscopy with Atomic Resolution

ABSTRACTRecently, we have developed Non-Contact Scanning Nonlinear Dielectric Microscopy (NC-SNDM) with a new height-control technique utilizing higher order nonlinear dielectric constant detection (ε(4) signal). In theoretically, NC-SNDM has quite high height sensitivity against the gap between tip and sample as well as STM technique and the simultaneous observation of the topography and ferroelectric polarization (local dipole moment) distribution with atomic resolution has been expected. To confirm such performance of NC-SNDM with atomic resolution, UHV-SNDM was developed and Si(111) cleaned surface was chosen as a specimen. As a result, we have succeeded in observing Si(111) 7×7 atomic structure. Moreover, distribution of tunneling current and lowest order nonlinear dielectric signal ε(3) could be observed simultaneously. To the best our knowledge, this is the first successful demonstration of the atomic resolution achievement in dielectric microscopy techniques.

INV-1 Scanning nonlinear dielectric microscopy with super-high resolution

INV-1 Scanning nonlinear dielectric microscopy with super-high resolution

Realization of 10Tbit∕in.2 memory density and subnanosecond domain switching time in ferroelectric data storage

Nanosized inverted domain dots in ferroelectric materials have potential application in ultrahigh-density rewritable data storage systems. Herein, a data storage system is presented based on scanning nonlinear dielectric microscopy and a thin film of ferroelectric single-crystal lithium tantalite. Through domain engineering, nanosized inverted domain dots have been successfully formed at a data density above 10.1Tbit∕in.2 and subnanosecond (500ps) domain switching speed has been achieved. Moreover, actual information storage is demonstrated at a density of 1Tbit∕in.2

Investigation of Three-Dimensional Domain Structure in LiTaO3 by Scanning Nonlinear Dielectric Microscopy

The three-dimensional domain configuration of multidomain LiTaO3 is revealed by scanning nonlinear dielectric microscopy (SNDM). SNDM can measure the polarization components both perpendicular and parallel to the surface of a specimen. These techniques are applied to both congruent and stoichiometric LiTaO3 crystals. The images obtained by SNDM measurements allow us to confirm the various domain features of LiTaO3 and to understand both similarities and differences between congruent and stoichiometric compositions.

Ultrahigh-Density Ferroelectric Data Storage with Low Bit Error Rate

Actual information data were recorded on a LiTaO3 single-crystal medium using a data storage system based on scanning nonlinear dielectric microscopy. For increasing recording density and reducing bit error rate, conductive-diamond-coated probes with a sharp tip and thin recording media were prepared. The domain-switching characteristics of virgin and prepolarized recording media were compared. The conditions of pulse voltage for writing were optimized. As a result, actual information data containing 128 ×128 bits were recorded at an areal density of 258 Gbit/inch2 without bit errors; thus, the bit error rate was calculated to be less than 1 ×10-4.

Ultrahigh-Density Ferroelectric Data Storage Based on Scanning Nonlinear Dielectric Microscopy

Ferroelectrics have generated considerable interest as promising storage media. In this paper, an investigation of ultrahigh-density ferroelectric data storage based on scanning nonlinear dielectric microscopy (SNDM) is described. For the purpose of obtaining fundamental knowledge on high-density ferroelectric data storage, several experiments on nanodomain formation in a lithium tantalate (LiTaO3) single crystal were conducted. As a result, a very small inverted domain with a radius of 6 nm was successfully formed in stoichiometric LiTaO3 (SLT), and a domain dot array with an areal density of 1.5 Tbit/in.2 was formed on congruent LiTaO3 (CLT). Moreover, it was found that fast nanosecond domain switching could be achieved by reducing the thickness of a CLT plate sample. Additionally, the prototype high-density ferroelectric data storage system was developed. Using this system, writing data transfer rates were evaluated and 256×256 bit data were recorded with the areal densities of 258 and 717 Gbit/in.2

Three-Dimensional Measurement for Absolute Value of Polarization Angle by Scanning Nonlinear Dielectric Microscopy

A technique for measuring the absolute value of ferroelectric polarization angles by scanning nonlinear dielectric microscopy (SNDM) is proposed and demonstrated. In this experiment, a periodically poled LiNbO3 (PPLN), which has a three-dimensional domain structure, is observed. The measured polarization angles agreed well with the actual polarization orientations, and the obtained values of polarization angles allowed an accurate visualization of the microdomain structure in PPLN. Through this experiment, we confirmed that 3D SNDM, which can measure in both the vertical and lateral polarization directions, is a useful technique for the absolute evaluation of the three-dimensional polarization direction.

Demonstration of Dopant Profiling in Ultrathin Channels of Vertical-Type Double-Gate Metal-Oxide-Semiconductor Field-Effect-Transistor by Scanning Nonlinear Dielectric Microscopy

We demonstrate dopant profiling in ultrathin channels (UTCs) (Tc=18–58 nm) of vertical-type double-gate metal-oxide-semiconductor field-effect-transistors (DG MOSFET) by scanning nonlinear dielectric microscopy (SNDM). The vertical UTCs were fabricated by orientation-dependent-wet etching. Using ion implantation technology and subsequent furnace annealing, n+-p junctions, which correspond to the source/drain of the vertical-type DG MOSFET, were formed in the upper part of the UTC. To improve the accuracy of the vertical dopant profile in the UTC, the cross-section of the UTC was magnified by beveling with a small angle by chemical mechanical polishing. Using such a beveled sample, the dopant depth profile in the vertical UTC has been measured by SNDM with nanometer-scale resolution. On the basis of the measurements of the dopant profile, an effective channel length for the vertical DG MOSFET has also been estimated quantitatively.

Visualization of electrons and holes localized in gate thin film of metal SiO2–Si3N4–SiO2 semiconductor-type flash memory using scanning nonlinear dielectric microscopy after writing-erasing cycling

We applied scanning nonlinear dielectric microscopy and succeeded in clarifying the position of the electrons/holes in the gate SiO2–Si3N4–SiO2 (ONO) film of the metal-ONO-semiconductor-type flash memory after the write-erase cycling operation. The electrons were found in the Si3N4 part of the ONO film. The holes, on the other hand, were found in the Si3N4 film as well as at the bottom SiO2 film. We also showed that neither injected electrons nor injected holes accumulate during the write-erase cycling. This indicates that the remaining carrier in the ONO film is space charge and would not be expected to continue to increase infinitely with repeated injections and that most of the injected carriers would recombine with each other. After recombination, they exist separately and are electrically neutralized only.

Visualization of electrons and holes localized in the thin gate film ofmetal-oxide-nitride-oxide-semiconductor type Flash memory by scanning nonlineardielectric microscopy

By applying scanning nonlinear dielectric microscopy (SNDM),we identified the position of electrons/holes existing in the gateSiO2–Si3N4–SiO2 (ONO) film of the metal-oxide-nitride-oxide-semiconductor(MONOS) type Flash memory. The electrons were detected in theSi3N4 part of the ONO film. The holes, on the other hand, were found in theSi3N4 film as well asin the bottom SiO2 film.

Non-contact scanning nonlinear dielectric microscopy

Contact-type scanning nonlinear dielectric microscopy (SNDM) can measure thedistribution of linear and nonlinear dielectric properties of insulators with sub-nanometreresolution. SNDM, however, has a tip-abrasion problem, and this problem is one of theobstacles in obtaining a high-quality image.In this paper, in order to improve SNDM, we propose a non-contact scanning nonlineardielectric microscopy (NC-SNDM) which focuses on the nonlinear dielectric signal forcontrolling the non-contact condition. With the NC-SNDM technique, topographic andSNDM images were obtained successfully. Moreover, from the calculation results, it wasconfirmed that NC-SNDM has atomic-order sensitivity to the gap between the tip and thespecimen.

Three-dimensional observation of nano-scale ferroelectric domain using scanning nonlinear dielectric microscopy

AbstractThree-dimensional domain configuration of multi-domain LiTaO3 is revealed by Scanning Nonlinear Dielectric Microscopy (SNDM). SNDM can measure the polarization components both perpendicular and parallel to the surface of the specimen. These techniques are applied to the both congruent and stoichiometric LiTaO3 crystals. The images obtained by SNDM measurements allow us to confirm the various domain features of LiTaO3 and to understand both similarities and differences between the congruent and stoichiometric compositions.

Super High-Density Ferroelectric Data Storage using Scanning Nonlinear Dielectric Microscopy

Ferroelectrics has generated considerable interest as promising storage media. In this paper, an investigation of ultrahigh-density ferroelectric data storage based on scanning nonlinear dielectric microscopy (SNDM) was carried out. For the purpose of obtaining fundamental knowledge of high-density ferroelectric data storage, several experiments on nanodomain formation in lithium tantalate (LiTaO3) single crystal were conducted. As a result, a very small inverted domain with a radius of 6 nm was successfully formed in stoichiometric LiTaO3 (SLT), and in addition, a domain dot array with an areal density of 1.5 Tbit/inch2 was formed on congruent LiTaO3 (CLT). Moreover, it was found that fast nanosecond domain switching could be achieved by reducing the sample thickness of CLT plate. Additionally, the first prototype high-density ferroelectric data storage system was developed. Using this system, writing data transfer rates were evaluated and 256×256 bit data were recorded with the areal densities of 258 Gbit/inch2 and 717 Gbit/inch2.

Visualization using scanning nonlinear dielectric microscopy of electrons and holes localized in the thin gate film of a metal–SiO2–Si3N4–SiO2–semiconductor flash memory

We have used scanning nonlinear dielectric microscopy to clarify the position of electrons and holes in the gate SiO2–Si3N4–SiO2 (ONO) film of a metal–ONO–semiconductor flash memory. The electrons were detected in the Si3N4 part of the ONO film, while the holes were found in the bottom SiO2 film as well as in the Si3N4 film. This suggests that the injected electrons and holes did not always recombine with each other.