Nanomechanical Effects

2021 ◽  
pp. 253-272
Author(s):  
C. Julian Chen
Keyword(s):  
Barrier Height ◽  
Contact Area ◽  
Soft Materials ◽  
Sample Surface ◽  
Soft Material ◽  
Measurable Effect ◽  
Tunneling Barrier ◽  
Hard Materials ◽  
Small Force ◽  
The Stability

This chapter discusses the effect of force and deformation of the tip apex and the sample surface in the operation and imaging mechanism of STM and AFM. Because the contact area is of atomic dimension, a very small force and deformation would generate a large measurable effect. Three effects are discussed. First is the stability of the STM junction, which depends on the rigidity of the material. For soft materials, hysterisis is more likely. For rigid materials, the approaching and retraction cycles are continuous and reproducible. Second is the effect of force and deformation to the STM imaging mechanism. For soft material such as graphite, force and deformation can amplify the observed corrugation. For hard materials as most metals, force and deformation can decrease the observed corrugation. Finally, the effect of force and deformation on tunneling barrier height measurements is discussed.

scholarly journals Finite Element Studies of the Influence of Pile-up on the Analysis of Nanoindentation Data

1996 ◽  
Vol 436 ◽  
Author(s):  
A. Bolshakov ◽  
W. C. Oliver ◽  
G. M. Pharr
Keyword(s):  
Finite Element ◽  
Contact Area ◽  
Peak Load ◽  
Soft Materials ◽  
Modulus Ratio ◽  
Hard Materials ◽  
Plastic Materials ◽  
Wide Range ◽  
Pile Up ◽  
Elastic Plastic Materials

AbstractMethods currently used for analyzing nanoindentation load-displacement data give good predictions of the contact area in the case of hard materials, but can underestimate the contact area by as much as 40% for soft materials which do not work harden. This underestimation results from the pile-up which forms around the hardness impression and leads to potentially significant errors in the measurement of hardness and elastic modulus. Finite element simulations of conical indentation for a wide range of elastic-plastic materials are presented which define the conditions under which pile-up is significant and determine the magnitude of the errors in hardness and modulus which may occur if pile-up is ignored. It is shown that the materials in which pile-up is not an important factor can be experimentally identified from the ratio of the final depth after unloading to the depth of the indentation at peak load, a parameter which also correlates with the hardness-to-modulus ratio.

The Effect of Surface Coating on Thermal Manikin’s Stability

2011 ◽  
Vol 413 ◽  
pp. 84-89
Author(s):  
Kai Yang ◽  
Ming Li Jiao
Keyword(s):  
Surface Coating ◽  
Surface Condition ◽  
Soft Materials ◽  
Fuzzy Mathematics ◽  
Thermal Manikin ◽  
Climate Chamber ◽  
Coating Materials ◽  
Hard Materials ◽  
The Stability ◽  
Effect Of Surface

Present thermal manikin is always enclosed by hard materials, and not covered with surface coating. So the surface condition of thermal manikin is very different with real body, which reduces thermal manikin’s stability. Therefore the research on thermal manikin’s surface coating and its effect on thermal manikin’s stability are necessary. In this paper, an appropriate material was selected to be thermal manikin’s surface coating and the satisfying result in improving the stability of thermal manikin was achieved. Firstly, five kinds of soft materials were selected to be candidate surface coating materials, which were EVA, HTV, TPU, medical used silicon rubber and cotton fabric. By lots of experiments and fuzzy mathematics theory, HTV was analyzed to have satisfying optimization performance than other materials and can be used as thermal manikin’s surface coating. Finally, to evaluate the effect of HTV surface coating on thermal manikin’s stability, comparative experiments were performed in climate chamber when thermal manikin covered with HTV surface coating and did not cover with HTV surface coating. Results show that HTV surface coating can obviously improve the stability of thermal manikin.

Local Tunneling Barrier Height on Si(111) Reconstructed Surfaces

1998 ◽  
Vol 37 (Part 1, No. 6B) ◽  
pp. 3782-3784 ◽  
Author(s):  
Nobuhiro Horiguchi ◽  
Kazunori Yonei ◽  
Masahiro Miyao
Keyword(s):  
Barrier Height ◽  
Tunneling Barrier ◽  
Reconstructed Surfaces

Tem Specimen Preparation by Mechanical Microthinning

1987 ◽  
Vol 115 ◽  
Author(s):  
H. K. Plummer ◽  
S. Shinozaki
Keyword(s):  
Soft Materials ◽  
Diamond Powder ◽  
Specimen Preparation ◽  
Ion Milling ◽  
Thin Specimen ◽  
Basic Premise ◽  
Mechanical Abrasion ◽  
Hard Materials ◽  
Transmission Electron ◽  
Lathe Tool

ABSTRACTMechanical abrasion has been used by the authors to prepare a variety of materials, mainly ceramics, which have been thinned to electron transparency. The basic premise of this technique is the rotation of a spherically shaped wood tool at right angles to a rotating 3mm specimen disk (∼100 μm thick). A slurry of 1/2 μm diamond powder in a glycerin vehicle thins the specimen and carries away the abraded matter. In addition to the wood tool other materials such as brass, teflon and polyethylene have been tried without success. Abrasion “marks” left on the thin specimen surface can be ignored in some situations or removed by a touch up ion milling at 3 keV for ∼1/2 hr. Recently, attempts to thin N+ implanted Al from the un-implanted side using a wood tool were found to be extremely time consuming, i.e. 60 hr or more. It was found that a spherical stainless steel tool produced a suitably thin transmission electron microscopy (TEM) specimen using glycerin as the vehicle and no diamond powder. Depending upon the pressure applied to the tool these specimens could be thinned in as little as 3 hr. The turning marks left by the lathe tool proved to be sufficient to thin the soft aluminum. From this result It appears that soft tools will thin hard materials and hard tools can be used to thin soft materials efficiently. A number of other specimens recently prepared using mechanical microthinning will also be presented.

Factors influencing the Action of Dust Insecticides

1950 ◽  
Vol 41 (1) ◽  
pp. 1-61 ◽  
Author(s):  
W. A. L. David ◽  
B. O. C. Gardiner
Keyword(s):  
Relative Humidity ◽  
Soft Materials ◽  
Experimental Procedure ◽  
Hard Materials ◽  
Dust Clouds ◽  
Factors Influencing ◽  
Before And After ◽  
Sudan Iii ◽  
Insecticidal Action ◽  
Gain Access

The methods used to investigate the properties of dusts are described and, in a theoretical section, the relevance of the various physical properties to insecticidal action are considered.In order to investigate the effect of toxic and non-toxic dusts on insects the experimental procedure was simplified to eliminate all difficulties associated with the formation of uniform dust clouds and deposits. In problems relating to the adherence of the dusts to insects the actual quantity of dust was measured either by weighing the insects before and after dusting or by dyeing the dust with Sudan III and determining the quantity colorimetrically. The experiments were all conducted under known conditions of temperature and humidity.Non-toxic dusts killed insects by causing them to lose water. Not all non-toxic powders were equally effective when conditioned to the same relative humidity. All were without effect at saturated humidity and became progressively more rapid in action as the humidity at which the test was carried out was decreased (p. 32).The non-toxic dusts caused the insects to lose water by abrading certain areas of the cuticle ; the more extensive the abrasion the more quickly the insects died (p. 27).To be effective as an abrasive the dust must be hard and finely ground and, perhaps also, sharply angular. Thus materials which ranked high in Moh's scale of hardness were in general more effective than soft materials and hard materials became quite ineffective unless they contained material below about 10 μ, diameter. Presumably the coarser materials could not gain access to the articulations, etc., where abrasion usually occurred. This effect can be seen clearly with carborundum powders. Sharply angular glass was more effective than the same powder converted into rounded spheres (pp. 25–31).

Inhomogeneous ohmic contacts: Barrier height and contact area determination

2012 ◽  
Vol 101 (5) ◽  
pp. 051604 ◽  
Author(s):  
Yang Li ◽  
Wei Long ◽  
Raymond T. Tung
Keyword(s):  
Barrier Height ◽  
Contact Area ◽  
Ohmic Contacts ◽  
Area Determination

Scanning Tunneling Microscopy (STM)/Local Tunneling Barrier Height (LBH) Studies on Cs Adsorption on a Pt(111) Surface

2002 ◽  
Vol 41 (Part 1, No. 7B) ◽  
pp. 5003-5007 ◽  
Author(s):  
Yoichi Yamada ◽  
Asawin Sinsarp ◽  
Masahiro Sasaki ◽  
Shigehiko Yamamoto
Keyword(s):  
Scanning Tunneling Microscopy ◽  
Barrier Height ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Tunneling Barrier

Detachment Criterion for Static Axisymmetric Bubbles on Horizontal Flat Surfaces

2009 ◽  
Author(s):  
Shong-Leih Lee ◽  
Chao-Fu Yang
Keyword(s):  
Contact Area ◽  
Contact Angles ◽  
Maximum Volume ◽  
Flat Surfaces ◽  
Bubble Detachment ◽  
Numerical Result ◽  
Detachment Criterion ◽  
The Stability ◽  
The Many ◽  
Maximum Contact

The static Young-Laplace equation is solved with the geometry method to yield the bubble shape on a horizontal flat surface under various contact angles. Multi-solution modes are found. Among the many possible equilibrium shapes of the bubble, however, only the fundamental solution mode could occur naturally. The value of VAR (volume to contact area ratio) could be a good measure for stability of equilibrium bubbles. The bubble becomes less stable when VAR increases. The numerical result reveals that in the course of bubble growth (i.e. volume increases) the VAR of the bubble increases linearly until the maximum contact area is reached. After that, VAR has a sharp increase due to a decreasing contact area. Beyond the maximum volume, equilibrium bubble does not seem possible. Based on the finding, it is postulated that bubble detachment occurs somewhere between the maximum contact area and the maximum volume according to perturbations from environment. However, the postulation seems to underestimate the stability of the bubble significantly for contact angles of larger than 160 degrees. A correction is proposed in the paper. Numerical result of bubble detachment criterion is fitted with polynomial functions of the contact angle.

scholarly journals Oxidized-monolayer tunneling barrier for strong Fermi-level depinning in layered InSe transistors

2019 ◽  
Vol 3 (1) ◽  
Author(s):  
Yi-Hsun Chen ◽  
Chih-Yi Cheng ◽  
Shao-Yu Chen ◽  
Jan Sebastian Dominic Rodriguez ◽  
Han-Ting Liao ◽  
...  
Keyword(s):  
Fermi Level ◽  
Schottky Barrier ◽  
Barrier Height ◽  
Schottky Barrier Height ◽  
Field Effect Transistors ◽  
High Mobility ◽  
Surface Oxidation ◽  
Tunneling Barrier ◽  
Experimental Realization ◽  
Gap States

AbstractIn two-dimensional (2D)-semiconductor-based field-effect transistors and optoelectronic devices, metal–semiconductor junctions are one of the crucial factors determining device performance. The Fermi-level (FL) pinning effect, which commonly caused by interfacial gap states, severely limits the tunability of junction characteristics, including barrier height and contact resistance. A tunneling contact scheme has been suggested to address the FL pinning issue in metal–2D-semiconductor junctions, whereas the experimental realization is still elusive. Here, we show that an oxidized-monolayer-enabled tunneling barrier can realize a pronounced FL depinning in indium selenide (InSe) transistors, exhibiting a large pinning factor of 0.5 and a highly modulated Schottky barrier height. The FL depinning can be attributed to the suppression of metal- and disorder-induced gap states as a result of the high-quality tunneling contacts. Structural characterizations indicate uniform and atomically thin-surface oxidation layer inherent from nature of van der Waals materials and atomically sharp oxide–2D-semiconductor interfaces. Moreover, by effectively lowering the Schottky barrier height, we achieve an electron mobility of 2160 cm2/Vs and a contact barrier of 65 meV in two-terminal InSe transistors. The realization of strong FL depinning in high-mobility InSe transistors with the oxidized-monolayer presents a viable strategy to exploit layered semiconductors in contact engineering for advanced electronics and optoelectronics.

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