This section has a mandate to realize SI unit metre and to establish facilities for nanoscale measurements and standardization
Principal Scientist:Dr. Rina Sharma
Scientist:Dr. Vijay Kumar Toutam
Junior Scientist:Ms. Girija Moona
Iodine frequency stabilised He-Ne laser operating 633nm, used to realise metre
SI unit metre is the length of path travelled by light in vacuum during a time interval of 1/299792458 of a second.
The CIPM recommends that the meter be realize by one of the following methods
- by means of the length l of the path traveled in vacuum by a plane electromagnetic wave in a time t; this length is obtained from the measured time t, using the relation l =c.t and the value of the speed of light in vacuum.
- by means of the wavelength in vacuum λ of a plane electromagnetic wave of frequency f; this wavelength is obtained from the measured frequency f, using the relation λ =c/f and the value of the speed of light in vacuum
- by means of one of the radiation from the list given by them, whose stated wavelength in vacuum or whose stated frequency can be used with the uncertainty shown, provided that the given specifications and accepted good practice are followed; and that in all cases any necessary corrections be applied to take account of actual conditions such as diffraction, gravitation, or imperfection in the vacuum.
*the value of the speed of light in vacuum c= 299 792 458 m/s
At CSIR-NPL, Iodine stabilised He-Ne laser operating 633nm( one from the CIPM listed lasers) is used to realise metre as per CIPM recommendations. This light radiation acts as the reference for dimensional measurements. Traceability to industrial measurements is disseminated through Standards of Dimension. Traceability of measurements is essential part of quality assurance.
Nanoscale Measurements e.g. Step height, Pitch ,Roughness, Thick film measurements etc
The present era is witnessing immature growth of nanotechnology. Quality assurance of nano particles, nano materials and nano devices used for nanotechnology is the need of the hour. Reference nano particles and nanostructures are required for traceability of measurements. This section has taken initiatives to develop standards and to establish traceable facilities for nanoscale measurements.
|Optical Profiler WYKO NT9800||
|Measurement capability : 3D surface measurement, film hickness, step height measurement Established under the project: ”Generic Development of Nanometrology for Nanotechnology at NPL-I”, funded by Department Of Electronics And Informatin Technology, Ministry Of Information Technology|
A3D Optical profiler With laser reference for direct traceability , has been Established under the project: ”Generic Development of Nanometrology for Nanotechnology at NPL-I”, funded by Department Of Electronics And Informatin Technology, Ministry Of Information Technology. This works on principle of Phase shifting interferometery and Vertical scanning interferometry . The profiler has Measurement capability for 3D surface measurement, film thickness, step height measurement. Activities related to development of nanoparticles and nanostructures for application as standards and memresistors and standardisation of AFM based nanometrology have also been initiated. Activities also include spreading awareness for the need of standardization in nanotechnology, in India Training programmes and Roun Robin experiments on nano metrology are organized from time to time. NPL, New Delhi is the first Lab in India to start such activities. There are several challenges in making nanoparticles with controlled size & structure with well define (2D&3D) dimension and evaluates their uncertainty in measurements for traceability. Fabrication of size controlled nanoparicles and 2D/3D nanostructures.
Study of Interfaces using AFM
1. Resistive switching random access memory (RAM) studies of Lanthanum Titanate (LaTiO3)
Resistive switching behavior of LaTiO3 films sandwiched between Ag, Au, bottom and Pt top electrodes were studied under Conductive Atomic force microscopy and probe station. Resistive switching with Ag electrodes showed the bipolar behavior. The role of AgO undergoing redox reactions is ascertained. In case of Au top electrode the breakdown is solely from LaTiO3 and the role of defects is given consideration for such behavior.
Figure 1. a) Resistive switching behavior of LaTiO3 with Silver top electrode. b) AFM image of Electric stress induced conducting filaments on LaTiO3 under high –ve sample bias.
2. Pin hole dominated electrical transport across LaTiO3/SrTiO3 polar hetero-junction
The experiment was done for four different diameters of electrodes say 400, 200, 50 and 5 μm respectively. Mostly schottky type behavior is observed for smaller diameter electrodes where as diode like behavior was observed for large area electrodes. The experiment was done for four different diameters of electrodes say 400, 200, 50 and 5 μm respectively. Mostly schottky type behavior is observed for smaller diameter electrodes where as diode like behavior was observed for large area electrodes.
Figure 2. Voltage dependent transport characteristics of LTO/STO interface showing two different current regimes for –ve bias.
Figure 3. Electrode dependent transport behavior across LaTiO3/SrTiO3 polar hetero-junction showing pin hole dominated electrical transport.
Figure 4. C-V measurements on LTO/STO interface for 400 um top electrode.