 Hello everyone, in today's class on advanced characterization technique, we are going to talk about a new characterization technique known as grazing incidence small angle x-ray scattering. In the last class, we had studied small angle x-ray scattering and we understood that how small angle scattering can help us about the distribution of sizes as well as shape of different particles and precipitates in a variety of materials. We also know that with the increase in research going on in nanotechnology, there is a lot of need for characterization technique that can be used to characterize small scale sizes and shapes on the surface and for that we need to use a technique which is essentially known as grazing incidence small angle x-ray scattering. Now if you remember, we had talked about grazing incidence while we talked about normal x-ray diffraction. So we can have either a normal incidence wherein the x-ray beam is incident on your sample in a reflection or in the transmission mode while in case of grazing incidence the beam is almost parallel and makes a very very small angle with the sample under consideration. The most important point that I would like to emphasize here onwards and that is why I am sticking on this particular slide is that what all techniques we are going to talk from here on in the course of this lectures is that are pretty sophisticated techniques and these are not the techniques which essentially are available you know in laboratory and like you just pick up your sample and take your sample over there to do the characterization. These are very sophisticated techniques and it is expected that you understand these techniques and get exposure to these techniques and then carry out your preliminary characterization using you know laboratory scale x-ray diffraction and other characterization tools and then you go to this advanced characterization techniques in order to solve your problem of importance. So let us start talking about grazing incidence small angle scattering in the present class. So as I had already mentioned grazing incidence small angle x-ray scattering is a variant of small angle x-ray scattering but it is used extensively for carrying out characterization on the surface it has it was developed by Levin et al in 1989. So you can realize that this technique is not something that is pretty old in fact there have been less than 15 years this technique has evolved. However, the development in this technique has been tremendous in the last 15 odd years and this technique is used extensively in almost all synchrotron sources all over the world because it is essentially applicable to study polymer films nanoparticles at interfaces implanted systems porous materials and deposited embedded or stacked semiconductor nanostructures. So you can see the tremendous implication that GSEC offers for characterization not only pertaining to semiconductor materials characterization but also for surface related issues like surface chemistry as well as catalysis. Another important aspect that has been investigated extensively using GSEC has been quantum dots which have been obtained by state of the art processing techniques like molecular beam epitaxy and liquid beam epitaxy. The most important part and the biggest advantage that GSEC offers is that we can really monitor the evolution of size, shape and morphology as well as the distribution on the plane or a 2D distribution while the deposition is occurring. So this way it offers us a tool to constantly monitor the evolution of these nanoscopic structures and the ability to play with the processing parameters or rather the deposition parameters to control the size, shape and morphology of the quantum or rather the nanoscopic entities to be processed. So not only does GSEC provide information about the morphology it also gives us information about the structure of the material. We won't be talking much about the structure part but I am just trying to touch upon this aspect just to let you know that GSEC can give us some information about the chemical structure as well as the morphological structure of the material. It gives us information in the same length scale as that of GSEC ranging from about 10 to 1000 and strong. In addition it can give us information about in plane since grazing incidence x-ray small angle x-ray scattering essentially is a surface characterization technique. It gives us information not only in the plane but also out of the plane or normal to the plane which is very very important for doing what is known as x-ray reflectivity and like I had already mentioned in the last class small angle x-ray scattering is complementary to say characterization techniques like SCM, TM and atomic force microscopy. Similarly GSEC is also complementary to something like SCM and atomic force microscopy. At the same time as we discussed in the last course or the last slide we figure out that GSEC is absolutely essential and absolutely state of the at when it comes to studying in situ studies on deposition of various materials. The best part about GSEC is that simply by varying the probe depth the depth to which the x-rays are penetrating we can study subsurface information. We can obtain significantly important subsurface information using GSEC. This is particularly important for studying subsurface damage caused during say something like implantation. The other important aspect which is very important which is very peculiar to GSEC is the ability to study in situ deposition and catalysis. At the same time like we had discussed in the last class that small angle x-ray scattering also provides us if not directly in a indirect way the chemical contrast between different phases we can also use GSEC and separate out chemically distinct entities in GSEC. However having said that I hope you appreciate that in grazing incidence small angle x-ray scattering the entire diffraction is occurring from a very very small volume of material and since the volume of material is very very small the kind of intensity that we are going to get is also going to be very very low and therefore we need a synchrotron source which gives us very high brilliance and intensity to obtain good amount of data using grazing incidence small angle x-ray scattering. In the last class we had discussed that for small angle scattering a synchrotron is essentially good. However you can always do small angle x-ray scattering using say a rotating anode or a microfocus tube. However in order to do grazing incidence small angle scattering it is almost always better to use a synchrotron source as the results obtained will be of high fidelity using a synchrotron source. So let us first try to understand what exactly or how really it works out in case of grazing incidence diffraction. So let us look at the grazing incidence geometry first. So if you look at the grazing incidence geometry here I have shown a thin film deposited over a substrate. Here you can see I have kind of exaggerated this incident angle say theta i and you can see how the incident beam on the substrate gets diffracted at the same time since it is incident on the sample at a very small angle we do get a diffuse scattering or due to specular reflection and this is if you can imagine it is going mostly perpendicular or at an angle away from the substrate plane. At the same time we also have a refracted beam which is going over here. Now I hope you appreciate depending on the incident angle we can have various situations. This is what is depicted in the next slide. Herein it is shown that for an angle theta incident angle theta which is less than a particular critical value which will be described in the next graph or next image you see there is no refracted beam. At the same time there is no beam along the surface. So there is just an incident beam which just bounces off from the surface of the substrate. So this is what happens below the critical limit which is the theta critical or theta c in case of any substrate or any material. However when you increase the theta incident which is over here you see that at a particular angle you do get a diffracted or reflected beam but in addition to that you get another refracted beam which just travels parallel to the surface of the substrate. So this the angle at which this particular phenomena occurs is known as the critical angle. This essentially ensures that if your theta is less than theta c you do not get any beam that gets refracted. However at theta equal to theta c you do get a condition where your beam does not get refracted but in fact it runs parallel to the substrate surface. Now you can imagine that if you are at theta equal to theta c you are going to get some information of the surface what all you are having on the surface. At the same time when you have angle which is more than theta which is more than the critical angle you do see that you do get a refracted beam also. So now you can imagine by just that by just changing the incident angle we can get a lot of information from the substrate. Imagine now let us go to the previous slide and look at a realistic situation wherein we not only have a substrate but also we have a thin film or say something like a quantum dots different morphology or say nanoparticles which are deposited on the surface of this substrate. So you can imagine that by choosing a proper combination or rather a proper value of theta we can get different conditions and obtain a lot of information which is pertaining to within the surface or normal to the surface or subsurface in grazing incidence geometry. Now this particular point is exploited extensively while doing grazing incidence small angle x-ray scattering. So in this figure we have shown how exactly a thin film is deposited on a substrate and how when a high intensity x-ray is incident at a particular angle say alpha i it gets reflected at a particular angle alpha f which is not shown over here but we will have a look at it later and there is another angle omega which is or rather xi in which there is in plane diffraction or rather in plane diffraction. So you can see that there is one condition where there is out of plane and in the other case there is diffraction within the plane which is along the direction parallel to the surface of the substrate and therefore the scattering vector is given by q parallel while the normal vector the scattering vector in the direction normal to the substrate plane is given by qz. Now how do we choose a critical angle for doing grazing incidence small angle x-ray scattering on a film deposited on a substrate. So I hope you appreciate that we can have two critical angles over here one for your film or a nanoscopic particles that are deposited on the surface and other for the substrate itself. So we choose depending on what kind of information we need obviously we are more interested when we are studying say a thin film or the nanoscopic deposited particles we are more interested in these particles and therefore we want all the information the diffraction information from these particles. So we want that we do get some information from we get maximum information from these particles therefore I hope you appreciate that my theta has to be greater than the theta critical from theta critical of the particles or of the thin film. Now this is very essential to ensure that my x-rays get refracted let us go back to the previous slide and have a look. So if my film if my theta is greater than theta c of the particles this will ensure that my x-ray is passing through the particle and this can give me a lot of information about the structure as well as morphology of the particles. However or thin film for that matter however if my theta c is higher than that of the theta critical for substrate then my information what I am getting for the nanoscopic entity either a thin film or a particle will also contain some information of the due to substrate refraction this is something that I want to avoid since my area of interest is only the nanoscopic film or the particles. Therefore I have to choose a critical angle for my thin film or nanoparticle on a substrate assembly such that the angle lies in between the theta critical of the substrate and that of the film. So that I get some signal from the rather most of my signal is coming from the thin film as well as I get some signal from the substrate but there is no refraction occurring in the substrate. Now this is also very very important if at all say I am doing implantation studies you know what happens during implantation during implantation we have heavy metal ions or heavy ions colliding with the substrate. So you can imagine that there will be a lot of damage caused in the substrate depending on the energy of the ions and this damage can vary depending on the depth right the distance from the surface. So if you want to study the subsurface damage that is occurring due to implantation you can always play with the incident angle the theta so that we get information from different depths. So this is one parameter which is used routinely to control the information the extent of information that we are getting during grazing incidents small angle x-ray scattering. So the entity that I was showing like how exactly it looks so this time around I have drawn a set of a bunch of rather small nanoparticles on a substrate. So we have the beam incident at alpha i and the wave vector corresponding to it at K i this gets scattered at K f the scattering vector is K f while the angle here is alpha f at the same time this is normal the scattering here is out of the plane at the same time there is going to be some scattering which is going to be in plane and this is shown over here which corresponds to this scattering vector Q y and angle of 2 theta f right. So we have these two scattering vectors Q z and Q y one out of the plane and Q y which is in the plane right so we get information all the information related. So you know that Q y and Q z will be in the reciprocal space right but Q y will contain all the information corresponding to what is happening in the two dimensions while Q z or Q z will consider all the information in the reciprocal space in the direction normal to the surface of the substrate. So I have again another schematic which is shown over here borrowed from very nice review paper which have extensively followed by renowned etel. So this shows essentially the realistic picture of what exactly is happening during G-Sax. So you have the incident beam and you see all these nanoscopic things means we are really talking about very small dimensions means G-Sax is used to essentially probe very very small dimensions of the order of few nanometers. So the structure is essentially similar to like this and this essentially shows what kind of events that you can expect during G-Sax and what kind of signals that you can get. Here again it is shown you can see that this sample rotation is provided about omega just to improve the statistics and this is how and we can have note down the value over here note down the pattern the scattering pattern as a function of omega. So let us now go into and understand try to just touch upon the physics of grazing incidents small angle x-ray scattering well I would like to mention that it is a pretty involved subject and I am not going to touch upon all the details of you know the scattering or diffraction theory associated with grazing incidents small angle x-ray scattering. But what we are going to try and do is just to get a feel for things and see how the kind of knowledge that we have gained while deriving structure factor for normal diffraction as well as we derived what are known as the form factors right in the last class how these can be extended to understand how does grazing incidents small angle x-ray scattering works. So you know that incident x-rays are at alpha I are scattered along kf in the direction 2 theta f and alpha f right like if you go back to the your slide you see that you know there is this kf and there is 2 theta f which is kf in the direction theta alpha f and which is out of the plane as well as in the plane it is reflected at 2 theta f right. So this is what is given over here you can always define a corresponding scattering wave vector using the geometry as q x y z 2 pi by lambda and this particular matrix remember this is in 3D. Now if you remember in small angle x-ray scattering we also had a term which was q what we got was 4 pi by lambda and there was a sin theta term if I remember it correctly. Now I hope you appreciate that we talked about this in small angle x-ray scattering right like the angles we are talking about are going to be very very small and since the angles are going to be very very small in order to detect these very small angles that sample to the detector distance has to be very very large therefore we looked that you know even in small angle x-ray scattering this distance was as large as 1 meter. Now when we are talking about the grazing incident scattering the same rule applies and we have a sample detector distance as large as 1 to 4 meters. So this is quite huge however if you go to even what is known as grazing incidents ultra small angle x-ray scattering where the diffraction occurs at very very small angle less than certainly 1 degree you see the distance can be as large as 1 to 12 meters but this is only possible or rather only used when we are using a synchrotron light source. So you know that the scattering intensity in the lateral direction what all intensity that we are getting can be given is iq and this iq is related to the form factor f which is nothing but which carries the information of the shape of the sample in the reciprocal space and your sq which is known as the interference function this in fact is very similar to what is what we studied what is known as structure factor. Now this I hope you appreciate and understand that here we are talking only about 2D structures so what all structures we have in 2D they can have lead to a particular structure factor like we have for simple say FCC or BCC you can do that and in fact we will be going through one example over there but the most important point is so our sq carries the information about the spatial distribution right while the f carries the information about the shape of the particles right so the actual intensity that we are getting is a combination of these two and we know that this we had studied in the last class itself that the shape function what we are having so we can derive shape functions take the Fourier transform because remember what all in the real space what we are having the particle or your the particle or quantum dot for that matter is going to have a size shape and morphology in real space however you have to appreciate that the entire information is has to be mapped into the reciprocal space and therefore you we had studied that you know your reciprocal space is nothing but a Fourier transform of the real space right so all this shape size and morphology are going to be modulated in a particular way to obtain a particular Fourier transform so the size shape and morphology that we see in the real space is it is will be if you take a Fourier transform of this size shape you can get a corresponding Fourier transform which corresponds to a particular size shape of the particle in the reciprocal space at the same time when we talk about all this simple transformations you have to keep one thing in mind that one thing which you had taken for granted was that all this involved scattering only once and that too kinematic scattering so this is what is known as a Perth approximation however I hope you appreciate that in G. Sacks geometry the Perth approximation may not hold true now let me just go back and tell you what exactly is born approximation so if you look at this particular image you can see that you know you just have one condition so there is one scattering right from one of these blocks or one of these dots of atoms or cluster of atoms which we see over here it can be a quantum dot or a nanoparticle however this is not the only case that can be expected like we can have a case where in let us assume that if you are incident at a different angle you get first reflected from the surface and then you bounce off and you go through this particle right there is a distinct probability of this happening let me just go and show you what exactly I mean so let if you go to the surface and we have say something like a pillar over here in case of born approximation we know that you know there is only single scattering while you know that in this kind of a case that is not necessarily true so we can have a situation where your incident x ray first gets reflected from the substrate and then it gets scattered right and I hope you appreciate that there can be a plenty of other options that can happen right like you can go like this get reflected okay or rather okay I will just have to dump this off I have made a mistake here okay so let us go back and have a look what exactly can happen in this geometry so this is something what we are having so this is a substrate right and say this is my something like a quantum dot so the born approximation essentially talks about single scattering event right single kinematic scattering however in this case I hope you appreciate that we can have a situation where the beam gets first reflected right from the substrate and then it gets scattered or it can get scattered through this one right through your substrate and then again get reflected right so all these multiple scattering events can occur in the grazing incidence geometry therefore we do not it is generally understood that this normal born approximation of single scattering is not at all valid and instead we do get different scattering events that lead to different scattering cross section and therefore there is a need to account for all this in the calculation now this is very complicated and I am not going to touch upon it but this is what is known as or these corrections considering all these events is accounted for in what is known as diffracted wave born approximation and it includes entire examples or entire category of reflection and refraction events that can be that can occur during grazing incidence small angle x-ray scattering right so let us again go back and look at the geometry so I am I see all the angles what we are talking about are pretty small the alpha i alpha c or alpha f are pretty small but just for the sake of simplicity I have kind of blown them up so that we can appreciate it so you can imagine that what actually is happening again the same image that your sample incident the x-rays are incident the wave vector kf it is incident at k i rather incident at an angle alpha i so what we see is there is a specular peak right now the specular peak as I hope you appreciate gives you a lot of information in the this is all along z right so this is qz and this alpha f that you see that is along qy so this gives you information about the in plane information right in the reciprocal space while qz gives you out of plane right so you get what is known as the specular peak now this specular peak gives you the information which is normal to the surface of the substrate right or film therefore it can give you information and specular as the name suggest can give you information about say something like the thickness of the film right like and this is classically known as x-ray reflectivity while the second peak that you get is essentially what is known as the yoneda peak which gives you the maximum scattering in the z direction now talking about specular peak I hope you appreciate that in the form factors calculation we had seen that how we get a lot of a bumps right like you get first a valley let me just go and draw it right so this is something what we had got earlier so this was i versus q and this was correlated with the size of the particle in our small angle x-ray scattering similarly we can use the specular peak that we are getting to measure say something like the period right if you are having thin film like what is the thickness of individual film so that information can be obtained using a specular peak I will talk about in details in the next slide but what I want to want you to remember is that the specular as well as the yoneda peak okay which occur which showed a fraction in the z direction gives you a lot of information about in a direction perpendicular to the substrate of the film okay so in these specular peak there is no information on the lateral surface there is only information for along the direction perpendicular to the plane of the substrate and it is best to measure the average thickness of all the particles of average thickness of the film that we are having and this gives rise to a technique known as x-ray reflectivity however I hope you appreciate that if you are interested only in obtaining information perpendicular to the direction or perpendicular to the plane of the substrate you do not really want any information about the plane of the surface and therefore the plane of the substrate and therefore to obtain very good x-ray reflectivity data you have to ensure that there is no scattering in this direction and this gives rise to a particular condition wherein you have 2 theta f equal to 0 so essentially this is achieved using this figure shows a very nice way wherein you increase alpha and alpha f right symmetrically to probe the reciprocal space perpendicular to the surface and while doing that you have to ensure that your 2 theta f is actually 0 so that all the information that we are getting is only along the z and this is very important because the interference now why do we get all these speckle pattern that I showed you this is due to interference between layer and substrate or if there are multi layer film you get interference between different layers or layer and vacuum if there is only one layer and this gives rise to interference pattern like we have we get during say a Young's double slit experiment and this leads to a maxima and minima and this interference pattern can be used again remember what information we are getting is in reciprocal space but once we converted to real space we do get information about say thickness of the film so these are known as cashing fringes and this gives us information about the layer thickness having said that not only for you know very homogeneous you know thickness or homogeneous films and we can determine thickness we can also use using a lot of assumptions x-ray reflectivity to analyze roughness as well as inter diffusion profiles in various interfaces so a schemat or rather experimental result of g-sax pattern of the cobalt 0.6 nanometer on silica 4.3 nanometer 60 such layers discontinuous multi layers shows it is you see it shows qy equal to 0 here is qy but you see your qz you see nice bragg diffraction peaks corresponding to cobalt so you can imagine that how you can use so I am not showing the analysis part over here but using this you see this is in the reciprocal space this will be say something like nanometer inverse so using this we can actually find out what is the period of the film okay so now let us go and have a look at the instrumentation part up to now when we talked about instrumentation of x-rays I hope you know what all is needed but having said that you one thing that needs to be remembered as I had already mentioned is that for grazing incident small angle x-ray scattering almost always a synchrotron is needed and therefore I am showing a schematic of the grazing incidence small angle x-ray facility with ultra high vacuum chamber at Bm32 beam line at the European synchrotron radiation facility so why do we have ultra high vacuum chamber well to utilize grazing incidence small angle scattering to its optimum now ultra high vacuum chamber is actually ensures that we can do a lot of thin film deposition and that is what is shown over here so you can do a lot of deposition sources right and study the evolution of these nano structure will be it nano film or say quantum dots in situ and really observe how they are growing how they are growing in vacuum so this assembly essentially shows that from a synchrotron we get a nice coherent parallel ray of beam which is incident on your sample and you see over here we have a beam stopper because you know if there is a direct incident beam it can cause damage to our detector and you can see the g-sax detector is placed right at very small angle to the incident with respect to the sample and you see over here here we have this normal grazing incidence x-ray diffraction which is at a slightly angle at a slightly higher angle but you see the incidence over here for the grazing incidence small angle x-ray scattering is pretty small and this can be figured out as you see they are almost in the they are not in the same line but they make up very very small angle with the sample right so this shows another the same thing in a different assembly again note the distance between your sample and the detector is huge and there is a there should be a beryllium window over here so that your x-rays can pass and here you see that is almost normal you see how small the angle is right and you see here you get all the information in plane information over here straight away on your 2D detector while out of plane information is over here too perpendicular right this is where you will get your specular pattern and your you need a peak so again I am mentioning time and again that all these information these are all exaggerated figures you know these are all happening at a nanoscopic level and see this angle is very very small very very small and that is why that is the reason essentially why we keep this distance very very large right so that we are able to see some difference okay so I hope you appreciate what all is the overall structure of grazing incidence small angle x-ray scattering system and therefore these are not available in laboratories and are available on at various beam lines in a synchrotron source so how do they look like we talked about form factors and all form factors as well as the interference factor right the interference pattern right so it was rather let us go back and have a look so this is your interference function right so we have form factor and we have interference function so let us see now how actually they coincide right like this we had seen in case of small angles x-ray scattering that if the form factor is different how do we see different diffraction rather a different scattering pattern here in addition to the different scattering pattern we also get information about how those different particles or yeah those different dots are assembled in a 2d in along the 2d substrate so this is how what we will try to understand so the form factors of we know that if you have a particular shape in real space how it can get transformed into the reciprocal space so this is just a simple Fourier transform of the shape under consideration so here if we look in the first figure we see that if we have one a cylindrical shape we do get a particular pattern now I would like to mention that this takes into account the diffracted wave born approximation right diffracted wave born approximation which accounted for different reflection and refraction conditions so this diffracted wave born approximation ensures that you know this is the kind of pattern that we get now you know that if you are getting this kind of a pattern a particular kind of pattern this can be correlated with the shape of the particle right and you see there is a bit of periodicity now this periodicity comes in the reciprocal space because of various multiple scattering events right now if you go and have a spherical shape you do see that we get a completely different kind of patterns so see depending on the two shapes right a cylindrical versus a spherical we can get different form factors right in the reciprocal space the same case or similar case is shown for a half sphere as well as for a for a prism so here you can see how different it looks and depending on this particular form factor we can find out what is the shape of the particles at the same time I talked about right like how we are keeping the material or the nanoparticles in 2D can give rise to what is known as the interference function so therefore if you look at a simple hexagonal structure of say particles that means in other words if the particles are arranged forming a hexagonal lattice we get the variation in along say something like your alpha f and 2 theta f in this pattern so you do get these fringes now these fringes that we are getting have a particular periodicity because of the hexagonal structure now the actual scattering pattern that we are going to get has is going to be the superposition of this interference function and the form factor right like we had this equation f of q y q z square into s right that was your scattering intensity so this is where you see so if I have a hexagonal arrangement of my spherical patterns well I do get a pattern which corresponded to my spherical form factor right like which we had derived over here so here we have a spherical form factor but the weight is arranged the lattice is hexagonal so therefore there is a superposition of these 2 things and we do get a very different pattern right so now this form factor I hope you appreciate that once you get your experimental pattern what we need to do is we need to assume shapes or make a first guess do simulations and get a good match between the experimental and simulated pattern to comment something about the size and shape of the particle similar in you know information or similar patterns for now can we try to guess what exactly we are getting so I hope you appreciate that we are getting the same period or other yeah it is the same period so this has to be all hexagonal now if you look at this one now this to me looks like so this is what this is superposition of half sphere with the hexagonal one while this is superposition of half sphere the superposition of prism with the hexagonal lattice so therefore I hope you appreciate that for the last 2 scattering patterns particularly for the with and we are having a hexagonal arrangement however of particles however for the first case we are having a half sphere party or rather half sphere sitting at all the corners of the hexagon while for the second case which is shown over here we have a prism sitting at all the corners of the hexagon so here again I have chosen one particular example and try to show you how exactly we can see in situ growth of particles so here again we are having the growth of germanium on silicon 001 substrate right so here you see that as the sample or as the quantum dot is growing we do see that there is a change in the scattering pattern and also all these things can be confirmed by doing say AFM or scanning electron microscopy so we can see that with the deposition condition we can look at how the you know how the quantum dot is evolving in shape as well as size now I would like to emphasize that you know for carrying out SCM and all it is very difficult you cannot do it we have to stop at each and every stage and then do the sample however grazing incidence small angle x-ray scattering probably offers the only technique wherein you can monitor you know the evolution of a particular you know the growth of particles or catalysis or chemical reactions occurring at the surface in situ right so this is the only technique that gives you real in situ information okay so to summarize I hope you appreciate that grazing incidence small angle x-ray scattering technique is now well established to characterize morphology of nanoscopic and to a certain extent microscopic particles for microscopic particles we essentially don't really need grazing incidence small angle x-ray scattering but for nanoscopic particles this is probably the only technique to give you a lot of information while doing in situ experiments we get complete information about nanoparticle sizes shapes distribution faceting as well as spatial correlation however I would like to point out that this information is not you know a straight forward information like diffraction all the information that we are getting is in the diffracted space and that is that corresponds to the Fourier space right the best possibility of g-sax is the in situ studies they offer an excellent platform to study growth catalysis and self-organization having said that synchrotron radiation is almost necessary I will make a very strong statement and say that you know synchrotron radiation is necessary for doing good quality grazing incidence small angle x-ray scattering and having done grazing incidence small angle x-ray scattering it is always a good idea to confirm your results with say other techniques like scanning electron microscopy or scanning tunneling microscopy or AFM having said that grazing incidence small angle x-ray scattering though not available routinely offers a very sophisticated tool to study the structure of materials at the nanoscopic scale thank you