Browsing by Subject "Scanning Probe Microscopy"

Now showing 1 - 3 of 3

Open Access
Grating loaded integrated optical cantilevers
(2010) Karademir, Ertuğrul
Cantilever beams are the most important parts of standard scanning probe microscopy. In this work, an integrated optical approach to sense the deflection of a cantilever beam is suggested and realized. A grating coupler loaded on the upper surface of the cantilever beam couples the incident light to the chip, which is then conveyed through a taper structure to a waveguide to be detected by a photodiode. Deflections of the cantilever beam change the optical path and hence the total transmitted intensity. Finally an optical signal is produced and this signal is measured. Resonance peak of 27.2 Q factor is obtained, which could be further enhanced by proper vibration isolation and employment of vacuum environment.
Open Access
Integrated optical displacement sensors for scanning force microscopies
(2003) Kocabaş, Coşkun
In this thesis, we have studied the use of integrated optical waveguide devices acting as integrated displacement sensors on cantilevers for scanning probe microscopes. These displacement sensors include integrated optical waveguide devices such as Bragg gratings, ring resonators, race track resonators and waveguide Michelson interferometers fabricated on a cantilever to measure the displacement of the cantilever tip due to the forces between surface and the tip. The displacement of the cantilever tip is measured directly from the change of the transmission characteristics of the optical device. As the cantilever tip displaces, the stress on the cantilever surface changes the refractive index of the materials that make up the integrated optical device which cause variations in its optical transmission characteristics. We have also studied an optical waveguide grating coupler fabricated on the cantilever for the same purpose. In two different embodiments of this device, light is either coupled in or out of the waveguide via the waveguide grating coupler. The displacement of the cantilever alters the direction of the scattered light and measuring the power of the scattered light with a position sensitive detector allows for the detection of cantilever i tip displacement. The novel design proposed in this work provides very high displacement sensitivity of the order of 10−4˚A−1 .
Open Access
Investigation of lateral forces in dynamic mode using combined AFM/STM
(2007) Atabak, Mehrdad
In this Ph.D. work, we constructed a ¯ber optic interferometer based non-contact Atomic Force Microscope (nc-AFM) combined with Scanning Tunneling Micro- scope(STM) to study lateral force interactions on Si(111)-(77) surface. The in- terferometer has been built in such a way that its sensitivity surpasses that of the earlier versions used in normal force measurements. The improvement in the resolution of the interferometer has allowed us to use sub-Angstrom oscillation amplitudes to obtain quantitative lateral force measurements. We have observed single and double atomic steps on Si(111)-(77) surface in topography and lat- eral sti®ness images. This information allowed us to measure the lateral forces directly and quantitatively. We have also carried out lateral force-distance spec- troscopy experiments, in which we simultaneously measured the force gradient and tunneling current, as the sample is approached towards the tip. The lateral force?distance curves exhibit a sharp increase of the force gradient, just after the tunnel current starts to increase, while the sample is approaching to the tip. We observed only positive force gradients. In separate experiments, we imaged the Cu-TBPP molecules deposited on Cu(100) surface in normal and torsional mode in dynamic force microscope us- ing STM feedback, with a homemade tungsten cantilever. Our experiments have shown the possibility of manipulating molecules on surface using a vibrating can- tilever. However the forces involved in these experiments are not quantitatively measured due to limitations of the method.