Deflection signal

The lateral deflection signal should also be checked. If the lateral response is high or unstable, it is quite likely that the normal deflection is influenced, even though it might look stable. 

It is possible to identify a threshold amplitude, defined as the amplitude at which the contact breaks, and pull-off occurs, for part of the ultrasonic cycle. It can be identified as the amplitude at which the inflection occurs in the normal deflection signal. 

Chronodeflectogram — A deflection signal where the deviation angle (6) of a probe laser beam is plotted as a function of time. It is also called chronodeflectomet-ric profile or PBD transient and is usually characterized by the presence of the - PBD maximum (or minimum) during the time evolution of the deflection signal [i]. See also - chronodeflectometry. 

Chronodeflectometry (CD) — A - probe beam deflection method in which a - potential pulse is applied, usually from a potential where there is no reaction, to one where the reaction evolves completely to the formation of products. The time evolution of the deflection signal is sampled and plotted as a function of time, which is named chronodeflectogram [i]. 

Direct mirage effect — A deflection signal usually associated with photothermal experiments in which the deflected probe light beam passes on the same side of the photoilluminated -> interface [i]. See also - photothermal deflection spectroscopy. 

There is a convention used to describe the refraction of a probe laser beam that considers the deflection as negative if the beam deviates towards the electrode surface and positive when the opposite deviation occurs. The former corresponds to the generation (or releasing) of soluble species, while the latter is related to the consumption (or inclusion) of reactants during the electrochemical experiment. The deflection signal has the same sign than the refractive index gradient developed from the electrode surface to the solution [iv]. 

Voltadeflectometric peak — A maximum or a minimum of the deflection signal developed in a - cyclic voltadeflectogram. The peak is related to the maximal concentration gradients of soluble species at the probe beam position [i]. 

Set vertical deflection signal (difference signal Vertical A) to zero... 

Fig. 2.9 Schematic of photodetector and differential output signals. The top LCD display shows the vertical deflection signal and the lower panel the lateral signal, while the sum signal is displayed as a bar in the ellipse on the lower part of the round display (see schematic)...

The fine approach for CM is carried out by the controller in an automated fashion. Before this approach and the start of the experiment are explained, the photodiode position must be adjusted. The position of the photodiode is changed such that the lateral deflection signal is set to 0.0 V and the vertical difference signal is offset to -2.0 V. The vertical deflection setpoint is entered as 0.0 V in the computer menu. Upon contact with the surface as a consequence of a lowered... 

Fig. 3.38 Contact mode AFM height image of egg PC vesicles adsorbed on glass captured with an imaging force of 30 pN left) and 50 pN right). The halo in the fast scan direction right to left) indicates that the tip can no longer track the surface features accurately, when imaging force and noise of the deflection signal become comparable ( 30 pN in this case). When the imaging forces are increased to 50 pN, the surface is tracked better. The asymmetry of the features can be explained by tip convolution effects (asymmetry of the probe tip) [87]...

Figure 5. Relative amplitude at 1 MHz of laser beam deflection signal as a function of Al film thickness for a series of Al-on-Si and Al-on-Si02-on-Si films. Circles are experimental data, and curves are from the extended Opsal-Rosencwaig model.

The rapidity with which explosive vapours can he detected and the relatively fast relaxation of the cantilever when the vapour stream is turned off is shown in Figure 4. When the PETN stream is turned on for 10 s, a 40 nm deflection signal is observed. When the vapour stream is turned off, the cantilever is relaxed hack almost to the original position within 60 s. Another important observation from the data shown in Figure 4 is that the resonance frequency of the cantilever does not change significantly as a result of the small amount of PETN deposited in 10 s. The bending of the cantilever is still quite easily detected. 

The stress change can be determined directly fixim the optical-beam deflection signal. The stress change is given by Stoney s equation ... 

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