Application Compendium - Agilent Technologies

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Electrostatic force effects in AFM In microscopy, the compositional mapping of heterogeneous materials is based on recognition of dissimilar sample components. In AFM this is achieved by differentiating the probe-sample interactions at the locations with different mechanical (modulus, friction, adhesion, viscoelasticity, etc), magnetic, electric or other properties. Compositional mapping is the compelling industrial application for analysis of multicomponent materials and it will be advanced further as the contrast variations observed in AFM images will be interpreted quantitatively in terms of materials properties. Although the AFM-based mechanical studies are the most explored application area, this paper is focused on studies of local electric behavior of various samples. Both contact and oscillatory techniques are used for AFM-based electric characterization yet we will consider mostly oscillatory AM mode and only in some cases will mention its companion – the FM mode. In the experiment, as the oscillating probe, which initially vibrates at or near its first flexural resonance ωmech with amplitude A0, approaches the sample, first, it will sense van der Waals forces, which change the tip-sample force gradient and shift the probe resonance to lower-frequencies. In a non-dissipative case, this shift is the only effect changing the amplitudeversus-frequency (A-v-ω) dependence. In AM mode, the amplitude change at ωmech is employed by a feedback loop to keep the tip-sample interaction constant during surface profiling. On further approach toward the sample, the probe comes into intermittent contact and the topography and phase images are collected at set-point amplitude (Asp) chosen by the researcher. For a particular probe and chosen A0 the tip-sample force can be adjusted by varying Asp. The experiments can be performed either at low tip-sample forces – the condition for a most gentle and high-resolution imaging of surfaces, or at elevated forces – the condition for compositional imaging based on differences of local mechanical properties. 6 In many cases, the phase images obtained at elevated tip-sample forces are most informative for such qualitative analysis of heterogeneous samples. The situation becomes more complicated when the probe behavior is also influenced by electrostatic tip-sample interactions. In traditional AM studies the electrostatic forces between a conducting probe and a sample surface with local charges manifest themselves in many ways. The amplitude-vs-Z (AvZ) and phase-versus-Z curves will have a signature of longrange electrostatic interactions, which also impact imaging in the non-contact regime. Figures 1A-H illustrate these effects showing the AvZ curve and images taken at different Asp on the surface of a LiNb03 crystal with Ag particles deposited along a grain boundary. The AvZ curve demonstrates a gradual drop of amplitude at large tip-sample separations. The topography and phase images recorded at Asp, which is chosen along this part of the curve, show that on approach of the probe to the sample, the Ag particles are first detected in the phase image (grey circle). This is due to higher sensitivity of the A B C D E F G H 2 phase changes to long-range electrostatic forces between the charged Ag particles and the conducting probe. On further approach, the increasing attractive force leads to higher phase contrast, and the similar pattern appears in the topography images (red and green circles). At some probe-sample distance the oscillating tip comes into intermittent contact and the AvZ curve changes from the gradual decline to the abrupt one. At Asp along the steep part of the AvZ curve (blue circle) the topography image distinctively shows a granular morphology of the LiNbO3 surface and the string of Ag particles. The related phase image enhances the edges of the grains similar to the amplitude (error Figure 1A-H. Top – amplitude-versus-distance curve on LiNbO3/Ag surface. The topography (A, C, E) and phase images (B, D, F) at different Asp as marked by color dots.
signal) image indicating the overwhelming contribution of tip-sample mechanical interactions to the image contrast. In other words, in AM mode when the probe behavior is measured at single frequency (ωmech), the electrostatic forces dominate the probe response in the noncontact regime but their effect becomes negligible in the intermittent contact. The intermittent contact AM imaging of samples with charged locations can be “disturbed” by a voltage applied to a conducting probe as shown in Figures 2A-F. The images of semifluorinated alkane F(CF2)14(CH2)20H (further referred as F14H20) adsorbates on graphite exhibit strong contrast variations of several domains (one is outlined with a red circle) as the probe voltage is changing. When imaging was performed with a non-biased probe, the domains in the topography image were not distinguishable from their surrounding yet they exhibited different contrast in the phase images. The same locations became pronounced in the topography images once the probe was biased (+3 V and -3 V) with respect to the sample. This observation raises a question regarding true topography measurements in AM. The false topography contrast is often observed in AM studies of smooth heterogeneous surfaces where more adhesive regions are “elevated” compared to less adhesive ones. 7 This effect is a consequence of a shift of the probe resonance frequency by attractive tip-sample interactions. Therefore, a negative charge of the outlined domain can explain its appearance in Figures 2C, 2E. Actually, surface charges might influence the topography measurements even when a regular Si probe is applied. Such probes have some level of conductivity and the surface charge can induce mirror charges in the probe and the related attractive interaction. A compensation of the surface charge effect by a proper voltage applied to the probe will help reveal the precise topography. Figures 3A-B present another case when a voltage applied to the probe enhances a number of particles in the topography image of thermoplastic vulcanizate – the material, which contains carbon black buried inside a polypropylene and rubber blend. These changes are caused by electrostatic force between the probe and carbon black particles contributing to a conducting percolation network in this composite material. A subtraction of the topography images will show these particles with even higher resolution as A B C D E F Figure 2A-F. Topography (A, C, E) and phase (B, D, F) images of an adsorbate of semifluorinated alkane F14H20 on graphite. The images in (A)-(B) were obtained with a non-biased probe, the images in (C)-(D) were recorded with the bias voltage +3 V and the images in (E)-(F) – with the bias voltage of -3 V. A B Figure 3A-B. The topography images of thermoplastic vulcanizate obtained with a non-biased probe (A) and with the bias voltage of +3 V. 3
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MATERIALS TESTING AND RESEARCH SOLU
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When accuracy and reliability in me
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AGILENT TECHNOLOGIES APPLICATIONS F
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Figure 1. Agilent Cary 630 FTIR spe
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The calibration samples were measur
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Author Frank Higgins Agilent Techno
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Figure 1. The overlaid aliphatic be
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Author John Seelenbinder Agilent Te
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Figure 3. Sample is lightly pressed
Page 19 and 20: Author Dr. Mustafa Kansiz Agilent T
Page 21 and 22: microscopy provides for a factor of
Page 23 and 24: Standard ATR IR Image No Pressure (
Page 25 and 26: A visual inspection of the sample u
Page 27 and 28: Experimental Instrumentation To per
Page 29 and 30: Authors Jonah Kirkwood † and Must
Page 31 and 32: Spectra were collected from each lo
Page 33 and 34: Infrared mapping allows for multipl
Page 35 and 36: The spectra in Figure 2 are visuall
Page 37 and 38: Conclusion Agilent‟s Cary 610 FTI
Page 39 and 40: Authors Dr. Wayne Collins*, John Se
Page 41 and 42: The calibration curve obtained for
Page 43 and 44: Conclusion Select ‘Peak Ratio’
Page 45 and 46: Summary This method describes a pro
Page 47 and 48: Method configuration To determine t
Page 51 and 52: The calibration curve for the deter
Page 53 and 54: Figure 6. The MicroLab PC FTIR soft
Page 55 and 56: Summary An analytically representat
Page 57 and 58: Figure 3. The Irganox 1010 peak are
Page 61 and 62: The calibration curve and equation
Page 63 and 64: Select ‘Peak Ratio’ - from the
Page 65 and 66: Summary An analytically representat
Page 67 and 68: Figure 3. The GMS peak height absor
Page 69: Advanced Atomic Force Microscopy: E
Page 73 and 74: A dependence of surface potential o
Page 75 and 76: A B C Figure 6A-C. The topography (
Page 77 and 78: A B Figure 10A-C. The topography (A
Page 79 and 80: KFM with AM-FM operation in the int
Page 81 and 82: ibbons is only slightly different f
Page 83 and 84: References 1. G. Binnig, C.F. Quate
Page 85 and 86: Figure 1. AFM topographic image of
Page 87 and 88: 100nm 100nm 350nm 100nm Figure 3. A
Page 89 and 90: to perfect hexagonal patterns, whic
Page 91 and 92: Single-pass KFM studies have been k
Page 93 and 94: images due to the difference of the
Page 95 and 96: 0.5 V) of the nanowires. Additional
Page 97 and 98: appeared in the topography image. T
Page 99 and 100: of PSS component. TEM studies of mo
Page 101 and 102: Atomic Force Microscopy Studies in
Page 103 and 104: on graphite and MoS2 are shown in F
Page 105 and 106: A B C D Scan size: 5 µm. Scan size
Page 107 and 108: images of PEDOT:PSS blend, (PEDOT -
Page 109 and 110: Young’s Modulus of Dielectric ‘
Page 111 and 112: Figure 3. Young’s modulus as a fu
Page 113 and 114: Nanoindentation, Scratch, and Eleva
Page 115 and 116: The samples listed as “D” sampl
Page 117 and 118: Figure 6. Elastic modulus results f
Page 119 and 120: Figure 11. Elastic modulus results
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Sample B Figure 16. Scratch curves
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Conclusions Nanoindentation and scr
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measurement technique has been expl
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References 1. J.L. Hay, “Using In
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Theory The complex shear modulus (G
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References 1. Jain, S.K., Bhattacha
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LCCC relies on carrying out isocrat
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log Mp 5 4.6 4.2 3.8 0.5 15% Water
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Authors Wei Luan and Chunxiao Wang
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Table 1. Chemical Information of An
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Injection Volume Influence of Real
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translator into three modes on diff
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To identify the matrix influence on
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Authors Chun-Xiao Wang and Wei Luan
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Table 1. Polymer Additives in ASTM
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1 2 3 4 5 1 Tinuvin P 2 BHT 3 BHEB
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1 Tinuvin P 2 BHT 3 BHEB 4 Isonox 1
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Authors Edgar Naegele Agilent Techn
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Results and discussion To meet the
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Authors Melissa Dunkle, Gerd Vanhoe
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Experimental The analyses were perf
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Repeatability of the SFC/MS analysi
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Conclusion The combination of the A
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Introduction Phthalates form a grou
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The analytical method was applied t
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Introduction Bisphenol A (BPA) is a
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Preparation of standards BPA and BP
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Limit of Detection (LOD) and Limit
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Sample analysis The content of BPA
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The calibration for BPA and BPF, wh
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Author Stephen Ball Agilent Technol
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Results and discussion By operating
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Introduction The wavelength of UV r
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LC parameters Premixed solutions of
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Linearity A linearity study was per
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References 1. Dr. James H. Gibson,
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Instrumentation Columns: 2 x PLgel
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Authors Greg Saunders and Ben MacCr
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Authors Greg Saunders, Ben MacCreat
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Author Greg Saunders Agilent Techno
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Figure 5. Universal calibration cur
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Methods and Materials Conditions Co
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Materials and Methods A column set
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