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| '''Non-contact atomic force microscopy''' ('''nc-AFM''') is a mode of [[atomic force microscopy]], which itself is a type of [[scanning probe microscopy]]. In nc-AFM a sharp probe is moved close (order of Angstoms) to the surface under study, the probe is then [[raster scan]]ned across the surface, the image is then constructed from the force interactions during the scan. The probe is connected to a resonator, usually a silicon-cantilever or a quartz crystal resonator. During in measurements the sensor is [[Harmonic_oscillator#Driven_harmonic_oscillators|driven]] so that it oscillates. The force interactions are measured either by measuring the change in amplitude of the oscillation at a constant frequency just off resonance (amplitude modulation) or by measuring the change in resonant frequency directly using a feedback circuit (usually a [[phase-locked loop|PLL]]) to always drive the sensor on resonance (frequency modulation).
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| ==Modes of operation==
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| The two most common modes of nc-AFM operation, frequency modulation and amplitude modulation, are described below.
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| ===Frequency modulation===
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| Frequency modulation, introduced by Albrecht ''et al.'' in 1991,<ref name="AlbrechtGrütter1991">{{cite journal|last1=Albrecht|first1=T. R.|last2=Grütter|first2=P.|last3=Horne|first3=D.|last4=Rugar|first4=D.|title=Frequency modulation detection using high-Q cantilevers for enhanced force microscope sensitivity|journal=Journal of Applied Physics|volume=69|issue=2|year=1991|pages=668|issn=00218979|doi=10.1063/1.347347}}</ref>
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| is a mode of nc-AFM where the change in resonant frequency of the sensor is tracked directly, by always exciting the sensor on [[resonance]]. To maintain excitation on resonance the electronics must keep a 90° [[Phase_(waves)#Phase_difference|phase difference]] between the excitation and response of the sensor. This is either done by driving the sensor with the [[Atomic_force_microscopy#AFM_cantilever_deflection_measurement|deflection signal]] phase shifted by 90°, or by using an advanced phase-locked loop which can lock to a specific phase.<ref name="NonyBaratoff2006">{{cite journal|last1=Nony|first1=Laurent|last2=Baratoff|first2=Alexis|last3=Schär|first3=Dominique|last4=Pfeiffer|first4=Oliver|last5=Wetzel|first5=Adrian|last6=Meyer|first6=Ernst|title=Noncontact atomic force microscopy simulator with phase-locked-loop controlled frequency detection and excitation|journal=Physical Review B|volume=74|issue=23|year=2006|issn=1098-0121|doi=10.1103/PhysRevB.74.235439}}</ref> The microscope can then use the change in resonant frequency (<math>\Delta F</math>) as the SPM reference channel, either in [[Scanning_probe_microscopy#Constant_interaction_mode|feedback mode]], or it can be recorded directly in [[Scanning_probe_microscopy#Constant_height_mode|constant height mode]].
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| During frequency modulated images, an additional feedback loop is normally used to keep the amplitude of resonance constant, by adjusting the drive amplitude. By recording the drive amplitude during the scan (usually refereed to as the damping channel as the need for a higher drive amplitude corresponds to more damping in the system) a complementary image is recorded showing only non-conservative forces. This allows conservative and non-conservative forces in the experiment to be separated.
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| ===Amplitude modulation===
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| [[File:AFM Amplitude Modulation.svg|thumbnail| Change in resonant frequency of AFM sensor driven off resonance (amplitude modulation mode) causes a change in amplitude.]]
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| Amplitude modulation was one of the original modes of operation introduced by Binnig and Quate in their seminal 1986 AFM paper,<ref name="BinnigQuate1986">{{cite journal|last1=Binnig|first1=G.|last2=Quate|first2=C. F.|title=Atomic Force Microscope|journal=Physical Review Letters|volume=56|issue=9|year=1986|pages=930–933|issn=0031-9007|doi=10.1103/PhysRevLett.56.930|pmid=10033323|last3=Gerber|first3=C}}</ref> in this mode the sensor is excited just off resonance. By exciting the sensor just above its resonant frequency, it is possible to detect forces which change the resonant frequency by monitoring the amplitude of oscillation. An attractive force on the probe causes a decrease in the sensors resonant frequency, thus the driving frequency is further from resonance and the amplitude decreases, the opposite is true for a repulsive force. The microscopes control electronics can then use amplitude as the SPM reference channel, either in [[Scanning_probe_microscopy#Constant_interaction_mode|feedback mode]], or it can be recorded directly in [[Scanning_probe_microscopy#Constant_height_mode|constant height mode]].
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| Amplitude modulation can fail if the non-conservative forces (damping) change during the experiment, as this changes the amplitude of the resonance peak itself, which will be interpreted as a change in resonant frequency. Another potential problem with amplitude modulation is that a sudden change to a more repulsive (less attractive) force can shift the resonance past the drive frequency causing it to decrease again. In constant height mode this will just lead to an image artefact, but in feedback mode the feedback will read this as a stronger attractive force, causing positive feedback until the feedback saturates.
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| An advantage of amplitude modulation is that there is only one feedback loop (the topography feedback loop) compared to three in frequency modulation (the phase/frequency loop, the amplitude loop, and the topography loop), making both operation and implementation much easier. Amplitude modulation, however, is rarely used in vacuum as the [[Q factor|Q]] of the sensor is usually so high that the sensor oscillates many times before the amplitude settles to its new value, thus slowing down operation.
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| ==Sensors==
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| ===Silicon microcantilever===
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| Silicon microcantilevers are used for both contact AFM and nc-AFM. Silicon microcantilevers are produced from etching small (~100μm × ~10μm × ~1μm) rectangular, triangular, or V-shaped [[cantilever]]s from silicon nitride. Originally they were produced without integrated tips and metal tips had to be evaporated on,<ref name="AkamineBarrett1990">{{cite journal|last1=Akamine|first1=S.|last2=Barrett|first2=R. C.|last3=Quate|first3=C. F.|title=Improved atomic force microscope images using microcantilevers with sharp tips|journal=Applied Physics Letters|volume=57|issue=3|year=1990|pages=316|issn=00036951|doi=10.1063/1.103677}}</ref> later a method was found to integrate the tips into the cantilever fabrication process.<ref name="Albrecht1990">{{cite journal|last1=Albrecht|first1=T. R.|title=Microfabrication of cantilever styli for the atomic force microscope|journal=Journal of Vacuum Science and Technology A|volume=8|issue=4|year=1990|pages=3386|issn=07342101|doi=10.1116/1.576520}}</ref>
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| nc-AFM cantilevers tend to have a higher [[stiffness]], ~40 N/m, and resonant frequency, ~200 kHz, than contact AFM cantilevers (with stiffnesses ~0.2 N/m and resonant frequencies ~15 kHz).<ref>{{cite web|title=AFM Probes catalogue|url=http://www.nanoworld.com/afm-probes-catalog|work=Nanoworld|accessdate=7 September 2013}}</ref> The reason for the higher stiffness is stop the probe snapping to contact with the surface due to [[Van der Waals force]]s.<ref name="Giessibl1997">{{cite journal|last1=Giessibl|first1=Franz|title=Forces and frequency shifts in atomic-resolution dynamic-force microscopy|journal=Physical Review B|volume=56|issue=24|year=1997|pages=16010–16015|issn=0163-1829|doi=10.1103/PhysRevB.56.16010}}</ref>
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| Silicon microcantilever tips can be coated for specific purposes, such as a ferromagnetic coatings for use as a [[magnetic force microscope]]. By [[Doping (semiconductor)|doping]] the silicon, the sensor can be made conductive to allow simultaneous [[scanning tunneling microscope|scanning tunneling microscopy]] (STM) and nc-AFM operation.<ref name="GiessiblTrafas1994">{{cite journal|last1=Giessibl|first1=F. J.|last2=Trafas|first2=B. M.|title=Piezoresistive cantilevers utilized for scanning tunneling and scanning force microscope in ultrahigh vacuum|journal=Review of Scientific Instruments|volume=65|issue=6|year=1994|pages=1923|issn=00346748|doi=10.1063/1.1145232}}</ref>
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| ===qPlus sensor===
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| [[File:QPlusSchematic.svg|thumbnail|Shematic of qPlus sensor. Red and blue areas represent the two gold electrodes on the quartz tuning fork (light yellow).]]
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| The qPlus sensor is used in many [[ultra-high vacuum]] nc-AFMs. The sensor is made from a [[Quartz oscillator|quartz tuning fork]] from a wristwatch. The tuning fork is glued to a mount such that one tine of the tuning fork is immobilised, a [[tungsten]] wire, etched to have a sharp apex, is then glued to the free prong.<ref name="Giessibl1998">{{cite journal|last1=Giessibl|first1=Franz J.|title=High-speed force sensor for force microscopy and profilometry utilizing a quartz tuning fork|journal=Applied Physics Letters|volume=73|issue=26|year=1998|pages=3956|issn=00036951|doi=10.1063/1.122948}}, </ref><ref name="Giessibl1996">{{cite journal|last1=Giessibl|first1=Franz J.|title=Vorrichtung zum beruehrungslosen Abtasten einer Oberflaeche und Verfahren dafuer|journal=German Patent DE 19633546, August 20 1996, published Feb 26 1998}}</ref> The AFM deflection signal is generated by the [[Piezoelectricity|piezoelectric effect]], and can be read from the two electrodes on the tuning fork.
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| As the tungsten tip wire is conductive, the qPlus sensor can be used for combined STM/nc-AFM operation. The tip can either be electrically connected to one of tuning fork electrodes, or to a separate thin (~30μm diameter) gold wire.<ref name="MajzikSetvín2012">{{cite journal|last1=Majzik|first1=Zsolt|last2=Setvín|first2=Martin|last3=Bettac|first3=Andreas|last4=Feltz|first4=Albrecht|last5=Cháb|first5=Vladimír|last6=Jelínek|first6=Pavel|title=Simultaneous current, force and dissipation measurements on the Si(111) 7×7 surface with an optimized qPlus AFM/STM technique|journal=Beilstein Journal of Nanotechnology|volume=3|year=2012|pages=249–259|issn=2190-4286|doi=10.3762/bjnano.3.28|pmid=22496998|pmc=3323914}}</ref> The advantage of the separate wire is that it can reduce [[Crosstalk (electronics)|cross-talk]] between the tunnel current and the deflection channels, however the wire will have its own resonance, which can affect the resonant properties of the sensor. A solution to this problem is a qPlus sensor with one or several integrated service electrodes has been proposed. <ref name="Giessibl2013">{{cite journal|last1=Giessibl|first1=Franz J.|title=Sensor for noncontact profiling of a surface|journal=US Patent 8,393,009, priority Nov 23 2010, issued Mar 5 2013}}</ref>
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| The qPlus sensor has a much higher stiffness than silicon microcantilevers, ~1800 N/m<ref name="Giessibl2000">{{cite journal|last1=Giessibl|first1=Franz J.|title=Atomic resolution on Si(111)-(7×7) by noncontact atomic force microscopy with a force sensor based on a quartz tuning fork|journal=Applied Physics Letters|volume=76|issue=11|year=2000|pages=1470|issn=00036951|doi=10.1063/1.126067}}</ref> (tip placement further down the tine can lead to higher stiffness’s ~2600 N/m<ref name="SweetmanJarvis2011">{{cite journal|last1=Sweetman|first1=A.|last2=Jarvis|first2=S.|last3=Danza|first3=R.|last4=Bamidele|first4=J.|last5=Kantorovich|first5=L.|last6=Moriarty|first6=P.|title=Manipulating Si(100) at 5 K using qPlus frequency modulated atomic force microscopy: Role of defects and dynamics in the mechanical switching of atoms|journal=Physical Review B|volume=84|issue=8|year=2011|issn=1098-0121|doi=10.1103/PhysRevB.84.085426}}</ref>). This higher stiffness allows higher forces before snap to contact instabilities. The resonant frequency of a qPlus sensor is lower than that of a silicon microcantilever, ~25 kHz (Watch tuning forks have a resonant frequency of 32,768 kHz before tip placement), thus the speed of operation is usually slower. qPlus sensors also often have long tip wires, approaching the length of the sensor, leading to a movement of the apex which is no longer perpendicular to the surface, thus probing the forces in a different direction to expected.<ref name="StirlingShaw2013">{{cite journal|last1=Stirling|first1=Julian|last2=Shaw|first2=Gordon A|title=Calculation of the effect of tip geometry on noncontact atomic force microscopy using a qPlus sensor|journal=Beilstein Journal of Nanotechnology|volume=4|year=2013|pages=10–19|issn=2190-4286|doi=10.3762/bjnano.4.2|pmid=23400392|pmc=3566854}}</ref>
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| ===Other sensors===
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| Before the development of the silicon microcantilever, gold foil<ref name="BinnigQuate1986" /> or tungsten wires<ref name="MeyerAmer1988">{{cite journal|last1=Meyer|first1=Gerhard|last2=Amer|first2=Nabil M.|title=Novel optical approach to atomic force microscopy|journal=Applied Physics Letters|volume=53|issue=12|year=1988|pages=1045|issn=00036951|doi=10.1063/1.100061}}</ref> were used as AFM sensors. A range of designs of quartz crystal resonators have been used,<ref name="BartzkeAntrack1993">{{cite journal|last1=Bartzke|first1=K.|last2=Antrack|first2=T.|last3=Schmidt|first3=K. H.|last4=Dammann|first4=E.|last5=Schatterny|first5=C. H.|title=The needle sensor a micromechanical detector for atomic force microscopy|journal=International Journal of Optoelectronics|volume=8|issue=5/6|year=1993|pages=669}}</ref><ref name="HeydeKulawik2004">{{cite journal|last1=Heyde|first1=M.|last2=Kulawik|first2=M.|last3=Rust|first3=H.-P.|last4=Freund|first4=H.-J.|title=Double quartz tuning fork sensor for low temperature atomic force and scanning tunneling microscopy|journal=Review of Scientific Instruments|volume=75|issue=7|year=2004|pages=2446|issn=00346748|doi=10.1063/1.1765753}}</ref> the most famous is the above mentioned qPlus sensor. A new development which is getting attention is the KolibriSensor®,<ref name="TorbrüggeSchaff2010">{{cite journal|last1=Torbrügge|first1=Stefan|last2=Schaff|first2=Oliver|last3=Rychen|first3=Jörg|title=Application of the KolibriSensor® to combined atomic-resolution scanning tunneling microscopy and noncontact atomic-force microscopy imaging|journal=Journal of Vacuum Science and Technology B|volume=28|issue=3|year=2010|pages=C4E12|issn=10711023|doi=10.1116/1.3430544}}</ref> using a length extensional quartz resonator, with a very high resonant frequency (~1 MHz) allowing very fast operation.
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| ==Force measurements==
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| ===Force spectroscopy===
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| Force spectroscopy a method to measure forces between the tip and the sample. In this method the topographic feedback loop is disabled, and the tip is ramped towards the surface, then back. During the ramp the amplitude or frequency shift (depending on the mode of operation) is recorded to show the strength of the interaction at different distances. Force spectroscopy was originally performed in amplitude modulation mode,<ref name="JarvisYamada1996">{{cite journal|last1=Jarvis|first1=S. P.|last2=Yamada|first2=H.|last3=Yamamoto|first3=S.-I.|last4=Tokumoto|first4=H.|last5=Pethica|first5=J. B.|title=Direct mechanical measurement of interatomic potentials|journal=Nature|volume=384|issue=6606|year=1996|pages=247–249|issn=0028-0836|doi=10.1038/384247a0}}</ref> but is now more commonly performed in frequency modulation. The force is not directly measured during the spectroscopy measurement, instead the frequency shift is measured which must then be converted into a force. The frequency shift can be calculated from a known tip sample force, <math>F_{ts}</math>, by:
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| <math>\Delta f = \frac{f_0}{kA^2}\langle F_{ts}q'\rangle \,</math>
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| where <math>q'</math> is the tip's oscillation from its equilibrium position, <math>k</math> and <math>f_0</math> are the sensors stiffness and resonant frequency, and <math>A</math> is the amplitude of oscillation. The angle brackets represent an average of one oscillation cycle. However, turning a measures frequency shift into a force, which is necessary during a real experiment, is much more complicated. Two methods are commonly used for this conversion, the Sader-Jarvis method<ref name="SaderJarvis2004">{{cite journal|last1=Sader|first1=John E.|last2=Jarvis|first2=Suzanne P.|title=Accurate formulas for interaction force and energy in frequency modulation force spectroscopy|journal=Applied Physics Letters|volume=84|issue=10|year=2004|pages=1801|issn=00036951|doi=10.1063/1.1667267}}</ref> and the Giessibl matrix method.<ref name="Giessibl2001">{{cite journal|last1=Giessibl|first1=F. J.|title=A direct method to calculate tip–sample forces from frequency shifts in frequency-modulation atomic force microscopy|journal=Applied Physics Letters|volume=78|issue=1|year=2001|pages=123|issn=00036951|doi=10.1063/1.1335546}}</ref>
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| For measurements of chemical forces the effect of the long range Van der Walls forces must be subtracted from the frequency shift data. Originally this was done by fitting a power law to the long range 'tail' of the spectrum (when the tip is far from the surface) and extrapolating this over the short range interaction (tip close to the surface). This fitting, however, is very sensitive to where the cut-off between long and short range forces is chosen, causing results of questionable accuracy. Usually the most appropriate method is to perform two spectroscopy measurements, one over any molecule under study, and a second above a lower section of the clean surface, then to directly subtract the second from the first. This method is not applicable to features under study on a flat surface as no lower section may exist.
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| ===Grid spectroscopy===
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| Grid spectroscopy is an extension of force spectroscopy described above. In grid spectroscopy multiple force spectra are taken in a grid over a surface, to build up a three dimensional force map above the surface. These experiments can take a considerable time, often over 24 hours, thus the microscope is usually cooled with [[liquid helium]] or an atom tracking method is employed to correct for drift.<ref name="RaheSchütte2011">{{cite journal|last1=Rahe|first1=Philipp|last2=Schütte|first2=Jens|last3=Schniederberend|first3=Werner|last4=Reichling|first4=Michael|last5=Abe|first5=Masayuki|last6=Sugimoto|first6=Yoshiaki|last7=Kühnle|first7=Angelika|title=Flexible drift-compensation system for precise 3D force mapping in severe drift environments|journal=Review of Scientific Instruments|volume=82|issue=6|year=2011|pages=063704|issn=00346748|doi=10.1063/1.3600453|pmid=21721699}}</ref>
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| ===Lateral force measurements===
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| It is possible to perform lateral force measurements using a nc-AFM probe oscillating normal to the surface under study.<ref name="TernesLutz2008">{{cite journal|last1=Ternes|first1=M.|last2=Lutz|first2=C. P.|last3=Hirjibehedin|first3=C. F.|last4=Giessibl|first4=F. J.|last5=Heinrich|first5=A. J.|title=The Force Needed to Move an Atom on a Surface|journal=Science|volume=319|issue=5866|year=2008|pages=1066–1069|issn=0036-8075|doi=10.1126/science.1150288|pmid=18292336}}</ref> This method uses a similar method to force spectroscopy except the tip is moved parallel to the surface while the frequency shift is recorded, this is repeated at multiple heights above the surface, starting far from the surface and moving closer. After any change to the surface, for example moving an atom on the surface, the experiment is stopped. This leaves a 2D grid of measured frequency shifts. Using the an appropriate force spectroscopy calculation each of the vertical frequency shift vectors can be converted into a vector of forces in the ''z''-direction, thus creating a 2D grid of calculated forces. These forces can be integrated vertically to produce a 2D map of the potential. It is then possible to differentiate the potential horizontally to calculate the lateral forces. As this method relies on heavy mathematical processing, in which each state assumes a vertical motion of the tip, it is critical that the sensor is not angled, and that the tip length is very short compared to the length of the sensor.<ref name="StirlingShaw2013" />
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| ==Notable results==
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| * nc-AFM was the first form of AFM to achieve true atomic resolution images, rather than averaging over multiple contacts, both on non-reactive and reactive surfaces.<ref name="Giessibl2003">{{cite journal|last1=Giessibl|first1=Franz J.|title=Advances in atomic force microscopy|journal=Reviews of Modern Physics|volume=75|issue=3|year=2003|pages=949–983|issn=0034-6861|doi=10.1103/RevModPhys.75.949}}</ref>
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| [[File:IBM Zurich Press Release AFM Image Penacene Aug 2009.jpg|thumbnail|nc-AFM image of Pentacene taken in [[IBM Zurich Research Laboratory|IBM Zurich]]]]
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| * nc-AFM was the first technique to directly image chemical bonds in real space,<ref name="GrossMohn2009">{{cite journal|last1=Gross|first1=L.|last2=Mohn|first2=F.|last3=Moll|first3=N.|last4=Liljeroth|first4=P.|last5=Meyer|first5=G.|title=The Chemical Structure of a Molecule Resolved by Atomic Force Microscopy|journal=Science|volume=325|issue=5944|year=2009|pages=1110–1114|issn=0036-8075|doi=10.1126/science.1176210|pmid=19713523}}</ref> see inset image. This resolution was achieved by picking up a single [[carbon monoxide|CO]] molecule on the apex of the tip.
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| * nc-AFM has been used to probe the force interaction between a single pair of molecules.<ref name="ChiutuSweetman2012">{{cite journal|last1=Chiutu|first1=C.|last2=Sweetman|first2=A. M.|last3=Lakin|first3=A. J.|last4=Stannard|first4=A.|last5=Jarvis|first5=S.|last6=Kantorovich|first6=L.|last7=Dunn|first7=J. L.|last8=Moriarty|first8=P.|title=Precise Orientation of a Single C_{60} Molecule on the Tip of a Scanning Probe Microscope|journal=Physical Review Letters|volume=108|issue=26|year=2012|issn=0031-9007|doi=10.1103/PhysRevLett.108.268302}}</ref>
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| ==References==
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| {{reflist}}
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| {{SPM2}}
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| [[Category:Scanning probe microscopy]]
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| [[Category:Intermolecular forces]]
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| [[Category:Scientific techniques]]
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Then, at the end of the service, I gave an altar call for people struggling with sexual issues. For the most part, on a day to day basis, we see only this side of the veil. It is possible to find the brand new definition of sexual intercourse and passion. Performers in these early photograph and film recordings usually thought we would remain anonymous to avoid legal sanction and social approbation. I had a chance to sit down with sex writer Rachel Khona, who understands from first-hand experience what it's like when you're dating a porn addict. Or you can also subscribe for Gay Videos Membership. Yes, it will take time and persistent application of certain principles and yes there will most likely be some slips along the way but the desired change can be realized.
You might think of looking at the porn as soon as they leave or go to sleep, and you might have been caught looking at porn before. To the porn market it can be like no cost promotion. Humans evolved this ability in order to compel us to do the things that make us feel good – like eating and having sex. It is not that all cookies are bad; there are some cookies that are good. If you want to see real attendance problems, go back to the supposed 'Golden Era: of baseball. Keywords or phrases are tools used in internet marketing to achieve better rankings in search engines. Because there are millions of fans of porn flicks worldwide, of course, porn fans always make means and measures to find out more about the top porn stars of their choice.
If possible you can meet community health researcher for possible advice and prescriptions for appropriate treatments. It means that several LAN cables can connect with the router in order for the other users to get internet access. The whole documentary rested on a vague belief that harm was in fact proven, not least her call for the industry to pay for sex education in the same way alcohol producers pay for facilities for alcoholics. In this way, it gradually changes your thought patterns from negative to positive and unrealistic to realistic. According to a release from the FBI, Schaffner used to be a Maryland based licensed clinical professional counselor, while Lutts was a pediatric nurse in San Diego. - Block Porn Keep your PC clean and Safe: Porn websites always have virus or adware, by blocking porn websites, you can keep your PC clean and safe. A diverse crowd of people started gathering around 8pm, with the films slated to start when it was dark enough, around 9.
Mostly this is because of the new forms of pornography, which seem to shed a negative light on their fringe associations, such as erotic photography. When they came across the material they simple had no cognitive defenses to deal with it. Some of our Congress members have determined that online porn addiction is as bad as crack or heroin addiction. She starred in popular titles like Internal Injections, Girlbang and Spunk�d 6. Justifying and rationalizing your behaviors are a natural part of this process but don't let these deter you from seeking help. If you loved this article so you would like to collect more info pertaining to free xxx hd porn videos generously visit our own web site. Both the top and the bottom of the funnel represent the cerebral cortex of our brains. The plasticity of the living matter of our nervous system, in short, is the reason why we do a thing with difficulty the first time, but soon do it more and more easily, and finally, with sufficient practice, do it semi-mechanically, or with hardly any consciousness at all.
These could be anger, embarrassment, shame, hurt or powerlessness. In fact, most adult entertainment aficionados think that the best adult materials can only be produced in the country. Addiction cannot be “hoped”, “willed”, or even “sentenced” away, it requires therapy based on established scientific principles. Sex is not evil, so why is it wrong to watch others have sex. Step 2: Set a passcode which enable app that stores photos. If you can develop the practice of giving your husband regular doses of skillful oral sex, he will be thrilled to the core. If the hijacker walks away from the table he's only out about ten bucks, but you're out your domain.