 Welcome to our transmission electron microscopy laboratory today I am going to talk about transmission electron microscope that is here what you are seeing is a 120 kV transmission electron microscope in the transmission electron microscope so we are using an electron beam to form the image because of the shorter wavelength nature of the electrons you are getting a high resolution in this transmission electron microscope for this purpose only we are going to electron microscope this part in this transmission electron microscope is a gun part in this gun we have cathode assembly and then anode is there here cathode is filament we are using lanthanum exaborate and tungsten filament by heating the filament you are getting a bunches of electrons these electrons are oscillated from the gun part to the anode ok so from anode it has to pass through the column to the bottom of the column ok so for that this electron should be oscillated with a high speed because the electrons are pausing through the column in the column is under very high vacuum otherwise it will interact with the air molecule there should be a scattering effect to avoid that the whole column is under high ultra high vacuum so from this here the top is cathode assembly is there the bottom is an anode from this part to here we have lenses are there the lenses are electromagnetic lenses so by applying current you can change the strength of the electromagnetic field by changing the strength of the electromagnetic lenses you can form the image and magnify the image ok so in this particular CM 12 transmission electron microscope they have introduced 4 elimination lenses that is condenser 1 condenser 2 mini condenser and condenser objective lens then from here to here all image formation lenses and magnification lenses are there so from this part we have an objective lens and intermediate lens and diffraction lens these 3 will form the image as well as the diffraction whenever the electron be hit the specimen you will get so many signals some of the electrons will pass through the specimen some of them will get scattered to a particular direction when it satisfies the black condition so that is called electron diffraction this will come from here to here by using this intermediate and diffraction lenses this image and diffraction is forming in different planes that is always the diffraction is forming in the back focal plane of the objective lens and then image is forming in the different plane so if you want to project the diffraction pattern you have to project the back focal plane of the objective lens by using a projector 1 and 2 lenses ok if you want to see the image plane you have to project the image plane and then you will get the image in the bottom so here what you are seeing is a screen this is the fluorescence screen if you see this there is a disc in that that is the fluorescence screen so you cannot able to see the electron image with your eye so for that this electron should hit the fluorescence screen immediately it will glow then you will see the image details ok so from this we can capture the image which is here we have a CCD camera with this so that image you can see in the monitor apart from this magnetic lenses the electron beam should pass through different apertures some of them are fixed aperture some of them are changeable aperture you can mechanically change the aperture so here this part is a condenser aperture part you can change the size of the condenser aperture by using this condenser aperture you can reduce the beam diameter ok but then this is an objective aperture nothing but we used to call this as a contrast aperture we used to change the contrast of the images this is called selected area diffraction aperture by using this you select the area of the specimen and then you can get the diffraction of this particular specimen so by using this transmission electron microscope you can get a structural information crystallographic information as well as the chemical information ok the chemical information you can achieve by energy dispersive x-ray analyzer ok by using a characteristic x-ray energy you can detect the elements present in that how you are getting is when the electron hit the specimen the x-rays will come out from the specimen ok there is each element has a characteristic x-ray energy that can be deducted by silicon lithium detector so silicon lithium is single crystal silicon on that lithium is doped lithium is a very light element so it will be very mobile in nature to hold it in the silicon crystal it should be cooled with liquid nitrogen temperature ok so from this this is a very important point in the transmission electron microscope the electron beam should oscillated heated by with the filament the electrons will bunches of electrons will come out and then it has to come through the lenses through this aperture and then it has to pass through the specimen ok the beam should pass through the specimen this portion is the specimen inserting position this part is called a goniometer so if you see this this is the specimen holder because the electrons is passing through the specimen your specimen thickness is very very very important you have to use a ultra thin specimen ok so for that different methods are there to prepare the specimen so your specimen should not exceed 100 to 150 nanometer thickness otherwise the electron will stop here itself ok to avoid that you have to make this specimen to 100 to 150 nanometer thickness by different methods for conductive material we have to go for electrolysis method and then for non-conductive material we used to go for iron milling by ionization process will thin the specimen for your powder sample we used to disperse the powder in on this grid that is called carbon coated copper grids ok so this whole instrument because we are using an electron magnetic lenses the hole is get heated up to avoid the heating up it will be circulated with 20 degree chilled water we have a chiller in that ok so this here I told this whole system is under high vacuum now I am going to show you the control controls of this transmission electron microscope see here the knobs are there this knob is a intensity knob you can converge and diverge the beam electron beam ok these two knobs are for tilting the specimen in both the direction by gonia materials as well as the holder tilt say this is the specimen holder for transmission electron microscope what you are seeing is a single tilt low background holder this is a double tilt holder so by using this holder you can rotate the specimen but that is a goniometer rotation and then you can tilt the specimen in the z axis direction ok the tilting of the specimen angle is shown here this is the heating holder by using this holder you can heat the specimen inside the microscope you can continuously observe what is the heat treatment effect in this this is the straining holder you can give this you can strain the sample inside the microscope ok while observing you can strain the sample and see the effect of that straining so we have two screws are there you loosen the screw and then you have to put the specimen here and then you can proceed the experiment this is a multiple specimen holder by using this holder you can load the specimen three specimen together and then you can view the specimen one by one this is a single tilt holder which I have loaded a aluminium foil see here you can see the specimen in this here the goniometer is there so I am going to insert the specimen so because I disturb the vacuum here chamber so now it is evacuating the specimen chamber this chamber is the specimen chamber if you observe it so it is now the pump is running so now it got evacuated I am inserting the specimen holder inside the microscope these all are the controls here see this is the layout of a vacuum system we have a rotary pump oil diffusion pump and Gatrian pump ok all are microprocessor controlled everything is isolated with pneumatic valves the pneumatic valves we are using a air compressor to control this pneumatic valves ok if you see this this portion is a control panel ok so you go here and then you see this this is a high tension now whenever you want to work in the microscope you have to switch on the high tension so the selection of high tension is very very important it depends on your specimen so here in this 120 kV is the maximum voltage you can use it that is an oscillating voltage so that depends on the kV what you are using your resolution is determined ok then this part I have already selected a 120 kV then what you have to do you have the heat the filament so thermionic emission ok so what I am doing is I am heating the filament you see that is just I am heating the filament you have to wait for till it is get a maximum electrons ok then from here you see here so many knobs are there so this is for magnification knob you can in this CM 12 microscope you can go to 8,20,000 magnification so this is a diffraction knob when you want to project a diffraction pattern from that back focal plane you switch on you just press this you will come to the diffraction mode these two are beam shifting x y direction you can shift the beam from x y direction then this knob is a focusing knob this is a step size this is fine focus you can change our course course and fine you can make it so this portion is called a multifunction knob this can be used for different purpose if you have an stigmatic problem you press this button stigmatic button and then you can adjust with this you can adjust the stigmatic correction so this is called a dark field image that I will show you in the monitor how the dark field image is coming though by pressing this you can tilt your gun slightly to the diffracted beam ok this is called an alignment because you have a very linear column you have to align the beam for that different alignment procedures are there starting with gun and then after that column and then everything from here to here so many lenses you can adjust the current and then you can align it and make proper beam should hit your specimen. I have already heated the filament so the electrons are coming out from the filament by heating the filament that is oscillated by high tension 120 kV then it will come towards the anode ok here all the lenses are positively charged so the attraction is towards the lenses and then you are seeing the image here. Now in this now already I have loaded an aluminum foil I am just going to show this aluminum foil the images from the aluminum foil you are seeing the images on the fluorescence screen then that will be seen in the monitor this is a objective aperture nothing but we used to call this as a contrast aperture what you are seeing this images without aperture when I insert the aperture you will see the difference see the contrast difference in this what you are seeing is a image of your aluminum foil ok then with this unit you can get the crystallographic information this is the selected area diffraction aperture see if we insert this aperture you can select the area from the image I have reduced the aperture size then again you can go to still lower aperture ok so the purpose of this aperture is you can select the area and go for diffraction this is the diffraction now if you press this selected area will give a diffraction pattern this is a diffraction pattern from the selected area when you select the transmitted beam to form the image that we used to call as a bright field image to form the image that is called dark field image I am using the transmitted beam to form the image this is called bright field image this is slightly out I am using the focusing knob to focus the beam nothing but I am adjusting the objective lens current see by using this translatory control now I am moving to the moving in the y direction the other side control is for x direction this area is darker some of this area is lighter so when the electron beam passing through the specimen some of them will get scattered nothing but get diffracted so those areas are less electrons hit that hit on that place here more electrons are hitting on the specimen ok because of that it is looks darker this is brighter in colour ok so this is why this if you take a diffraction from this area you will get a exact orientation so this is in orientation this is in another orientation now I am again coming to the diffraction mode so the previous one image is formed by the transmitted beam so by using an objective aperture I am going to select this beam ok so now I am going to select any one diffracted spot if you see this image some areas are getting highlighted this is darker in colour ok so what is happening is these areas are correspond to that particular plane particular diffraction pattern ok this will represent the particular diffraction spot ok so if you have any defect or anything so we can find out the particular plane where the defect is there by indexing the diffraction spot ok this image is called dark field image ok when you use the diffracted spot to form the image that is called dark field image if you use a transmitted beam to form the image that is called bright field image some collection of x-rays are here this correspond to energy versus intensity ok so what I am going to do is I am going to find out the elements what is that element see it belongs to aluminium so I am going to do this aluminium ok it is a commercially pure aluminium and then some copper in this this is a copper peak 8 point so copper peak is there you add it ok so see here now we can see this raising up you have to give some time for the collection ok ok and then I am going to stop it and then you quantity both the thing you can do it here so I am going to quantification I am going to the quantification of this elements present see now you see this this is the weight percentage and then atomic percentage both are you are getting from this pdx analysis energy dispersive x-ray analysis this unit it is here 200 kv tecnic unit ok this is also a transmission electron microscope working in 200 kv that is the only difference from the cm 12 so because using a 200 kv as an oscillating voltage your resolution is more higher ok because of the higher voltage you are getting a shorter wavelength then the resolution is very short that is 0.2 nanometer level you can resolve the specimen ok so the same working principle is same here same electron gun is there the emitter is lanthanum exaborate then by hitting the filament if you will get an electrons that will be oscillated by a high kv 200 kv then there is an anode then through that the electrons are pausing through different lenses all lenses are electromagnetic lenses apart from that the same type of condenser aperture objective aperture and then selected air diffraction aperture all this thing electron beam is pausing through these apertures so this portion is a specimen chamber same singleton to holder I have loaded here so the electron beam should pass through the specimen and then you will view the specimen in the fluorescence screen ok so the same way there is a CCD camera is there you will capture the image in the CCD camera and then you can see this in the monitor ok some controls are different here I will just want to show you that so here the left side control panel is for this there is a knob this is for controlling the intensity and then there is a stigmata control control is there there is a multifunction knob that is as in CM 12 we can do the stigmatism correction and then you can ship the beam everything you can done with this and then there is a track ball by using this you can move the intensity of the beam x x y direction there is a tilt control that is by tilting in this is a goniometer tilt condition knob this is a holder tilt knob so these things are optional you can select L1 L2 L3 L1 is for clean lift L2 is reset focus and then L3 is pot size reducing the spot size that is so these all are this is an optional by clicking it you can select whatever you want in this ok you see here all these things are intensity zoom all these things are there you can select whatever you want this this is a multifunction x direction then if you want to increase the magnification you have to use this knob to increase the magnification the same way coarse and fine focusing knob and then we when you press this will go to the dark field imaging if you want to go to the diffraction you can press this knob all this wobbler and eccentric focus is there so for a while tilting your area of interest should not go out of the optical axis for that you have to do the eccentric correction for this we are using these two knobs this one is also optional R1 R2 R3 you can select according to that so R1 is for screen dim we have selected R2 is for alpha wobbler R3 is for spot size that is beam diameter reducing you can go to a spot 1 2 like that increasing order so increasing the diameter you have to go to the reducing order this is a vacuum layout of this microscope there is a rotary pump and then IGP pump two IGPs are there because it is a very big column and then we have oil diffusion pump is there so this is 10 power minus 7 to 8 are you can achieve from this thing after getting the vacuum status you will see the values numerical values here we know it should come to gun should come nearly 23 then we have already selected high tension to 200 kV this is the 200 kV electron microscope so in 200 kV only you will get a maximum resolution then after that I have to heat the filament just pressing this knob now the filament is getting heated up okay you have to wait for some time there is there we have already given some time delay so it is getting heated up okay there here if you see this there is this the magnification at present I am in 250,000 magnification there is a spot size all these data are given here you can by using this knob you can change all these things okay we have to wait for some time to get the filament to heat what you are seeing is the image of your specimen so this is the powder sample see I have mentioned in CM12 there is copper mesh on that there is a fine coating of carbon film that is few nanometer thickness on the carbon film we disperse the powder if you see this there is a dark lines are there that is the mesh image okay that is the shadow of the mesh so in between you will see the squares inside the square you are seeing something some black black things are there no that is your specimen this is a joystick you can move the specimen from x y direction okay by using the joystick you select the specimen place okay so by using by moving this x direction y direction like this you can move all in all direction okay this is the joystick see now I am selecting this area okay right so what I am going to do is see I have selected by see this by moving this here and then here everywhere wherever you want you select by using this joystick okay the whole screen you can move like this okay right now by using this L1 button I am lifting the screen then you will see the image here this is a CNT powder carbon nanotubes powder so what you have to do know you have to select any one particle by increasing the magnification you see I am increasing continuously continuously like this then in this position you have to insert this aperture objective aperture to get a better contrast then you further increases you select any one fiber and you will see the difference that is what I am going to do is by using this now increase increase further increase further this is a carbon nanotube the distance is 200 nanometers this is a magnification of this carbon nanotubes I have increased it and focused it I got this you see here then I will go for further magnification okay see here further resolution nothing but further resolution you will this distance is 200 nanometer you will see the increase in the resolution this is 50 nanometer okay you will see this this is a carbon nanotube and then when I am going further to that you will see that this is a fine nanometer image see here this is a fine nanometer image what you are seeing is a lattice fringes okay so this is a carbon nanotube so the distance between these two line is 0.34 angstrom so in because we are using a 200 kV because the resolution is high that is shorter the wavelength higher the resolution okay so my higher because of the higher voltage so this is carbon lattice okay then if you see further see here this is again interest in high magnification then again come down so this is slightly lower magnification this is an 490 x kx nothing but this distance is 10 nanometer okay then if you see here see this same 10 nanometer area you can see this okay see here this is the lattice imaging this is the advantage of this 200 kV transmission electron microscope even if you go to 300 kV you can get even in the order of 0.1 nanometer level even further with the field emission gun you can get atomic resolution is possible okay next time showing is this is again 700 see again I am showing okay see this is seen 700 I just want to show some of the photographs which we have already taken with different samples okay just I am going to show you this one see here you will see this okay because it is a two phase alloy sample okay this is you will see the lattice of this two two lattices you can able to see it okay then we go here we see this this is a lattice imaging okay so in this by using this we have FFT facility in this this is called an FFT facility go to live FFT so you have to select any one area by putting an alt and this you have to select this square and then select the area like this okay sorry it is not clear okay then go to process then you go to live effect FFT you will get something here it is almost identical your diffraction pattern okay so this distance you can easily find out even if you if you move this you will see the difference in the diffraction pattern this is you see here it is in two phases are there if you zoom it you will see two two spots will be there here so if you go here also you can see this okay so if you go to this go to FFT okay then go to inverse see see the difference between these two lines okay there is a fine lines so when we have a profile is there okay so when you measure from this to this line okay you are getting a graph of this then you will see the spacing of this each line the small lines are there no so you will see the spacing of these lines so you can do like this you can find out so it should be see here you have to select properly otherwise you would not get the proper result so you have to select this see see this is see here from here to here so we are getting this this is the value of you have to select properly this is your resolution of your spacing see here it is given here okay so from here to here if you observe it here but it is very fine so because of that we cannot able to find out because still two nanometer only we can easily resolve it because it is lesser than that it is a indium silver alloy something they have the student brought it so this is the resolution you can find out by using this FFT option this is taken from our microscope this is a fine nanometer that is a maximum resolution you can get it even lesser than 0.2 nanometer we are resolving here this is the advantage of 200 kV electron microscope if you go to 300 kV even one angstrom resolution is possible this is an energy dispersive x-ray analyzer as per in CMTOL the same configuration is there we have a same silicon lithium detector to detect the x-rays that by using a characteristic x-ray energy energy we are we are detecting the elements so the spectrum developed here is belongs to AG okay silver okay so then apart from that some of the elements are there here we have to locate it some copper is there here see copper is there you load it okay by using this we can quantify it the qualitatively as well as quantitatively you can achieve the results by using a energy dispersive x-ray analyzer so you have to go for quantification you will get these things so this presence of elements silver is there copper is there then you will quantitatively you can find out the elements present in the particular sample