Patent Application
20140103582
The present invention relates to nano-structures capable of molecular scale influences. In particular it relates to devices containing a small opening, such as nano-pipets.
A hollow high aspect ratio sample, such as a nano-test-tube, with a tip that is closed off is secured in a particle beam device, such as a transmission electron microscope. The tip is engaged with the particle beam of the particle beam device until a hole opens up on the tip, thereby turning the high aspect ratio sample into a nano-pipet.
A nano-pipet having a hole that does not meet desired parameter values is secured in a particle beam device, such as a transmission electron microscope. The nano-pipet is engaged with the particle beam of the particle beam device to attain the desired values of the hole parameters.
These and other features of the present invention will become apparent from the accompanying detailed description and drawings, wherein:
Precise diameter holes at the end of a nano-test-tubes, often referred to as nano-pipets, find applications in a wide variety of endeavors in the fields of physics, biology, chemistry, and others. For example, nano-pipets may find uses for DNA sequencing. In order to distinguish individual molecules, the size of the nano-pipet hole, or opening, should be shrunk down to the sub-10 nm region. A process for reproducible production of nano-pipets with controlled hole sizes down to the nm regime would be useful for many applications.
Embodiments of the present invention teach nano-pipet fabrication. Embodiments of the invention allow to reproducibly produce nano-pipet holes, or openings, with precise desired characteristics, such as the diameter of the hole. The hole characteristics, or parameters, can be observed in real time during the fabrication and applied as feedback during processing. The embodiments teach the use of a particle beam device (PBD) in opening a hole in the tip of a high aspect ratio (HAR) sample, for instance a nano-test-tube, with the particle beam of the PBD. One may, of course, also take an existing nano-pipet and modify the hole.
The cross section of the hollow HAR sample typically, but necessarily, is circular. The hollow HAR sample 10 has a tip 31 that is closed off at the termination of the tapered portion 21. The term tapered portion it not meant to be understood in a limiting fashion. It is possible that the whole of the hollow HAR sample is tapered, or that the tapering is so short that it is practically indistinguishable from the tip.
The tip 31 in a typical embodiment of the present invention may be sharp, being in the regime of a few nm, possibly up to 30 nm, regime. The tip 31 of the tapered portion 21 may be characterized with tip parameters, such may be a wall thickness 42 of the hollow HAR sample 10 near the tip 31, and a tip angle 43, which is a measure of the degree of tapering. The wall thickness 42 may span a wide range of values. The wall thickness 42 may be as small as 0.5 nm to as large as being in the micrometer regime. The light hatching in the figure is only intended to mark empty space inside the hollow HAR sample. The hollow HAR sample may be regarded as a not fully formed nano-pipet, with the difference being that a nano-pipet has a hole at its tip.
In representative embodiments of the instant disclosure the hollow HAR sample may be made of drawn glass, or another quartz based material.
The hollow HAR sample 10 is inside a PBD 100.
The hollow HAR sample 10 is in such a position inside the PBD that the controllable particle beam 102 of the PBD is capable of engaging the tip 31 of the hollow HAR sample. This engaging by the particle beam 102 is done with such engaging parameters that a hole 11 opens up on the tip 31, whereby the hollow HAR sample 10 is transformed into a nano-pipet 101, shown in
The engaging parameters of the controllable particle beam 102 for the purposes of opening up the hole 11 may include particle beam intensity, beam diameter, duration of the engaging, and possibly others.
In representative embodiments of the instant disclosure the engaging particle beam 102 is an electron beam. With an electron beam, either in a TEM or an SEM, one may also image the tip 31, as is shown, for example, in
In representative embodiments of the instant disclosure the PBD is a TEM and the hollow HAR sample is a nano-test-tube made of drawn glass. The embodiments of the invention allow for high degree of precision and reproducibility in the nano-pipet fabrication. This is due to the ability of imaging the sample before, while, and after the hole forming process without the need to remove the sample from the PBD, or even from the sample holder. The same beam that is used to form the hole, is also used for the imaging that supplies the necessary parameters for an optimized hole. For the purpose of even more reproducibility and uniformity of holes, if after the beam engaging for creating the hole 11, the hole parameters are not of the desired values, one may repeat the engaging process by the particle beam 102, until one does attain the desired values of the hole parameters.
In alternate embodiments of the instant disclosure one may commence with a nano-pipet, which may have been produced by any method, and which has a hole parameter with a value that differs from the parameter's desired value. One may then engage the nano-pipet with the particle beam of the PBD to change the value and to attain the desired value for the hole parameter.
Typical engaging parameters in a TEM for an electron beam may be in the range of 30 kV to 400 kV with beam currents of nano to micro amperes, and with a beam diameter being the range of fraction of a nm to over a 1000 nm, typically to fit the dimensions of the tip 31, Representative engaging times may be as short as a few, maybe 5 seconds, up to a few minutes, but more typically not more than 1 minute.
It is assumed that for hole forming the main effect of the particle beam 102 engagement is that of heating the region of the tip 31 of the hollow HAR sample 10. However, the ambient conditions 110 inside the PBD may also influence the process of hole creation. It may be possible that the ambient conditions 110 affect the degree of heating due to the particle beam 102, it also may be possible that the ambient conditions 110 affect the hole formation through chemical effects. In any case in representative embodiments of the instant disclosure one would select the ambient conditions 110 inside the PBD 100 in such manner to facilitate the formation of the hole.
The ambient conditions 110 inside the PBD 100 that are purposefully selected for optimal hole formation may include a gas pressure range. Such pressure range may be chosen to between about 10−3 torr and 10−7 torr, but more typically between about 10−4 torr and 10−5 torr. One may also select the precursor gases that can be present inside the PBD while conforming to the chosen pressure range. Precursor gases for hole formation or modification may be selected from oxygen containing, or hydrogen containing, or halide containing gases, and their admixtures.
In the foregoing specification, the invention has been described with reference to specific embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present invention.
In addition, any specified material or any specified dimension of any structure described herein is by way of example only, without intent of restricting. Furthermore, as will be understood by those skilled in the art, the structures described herein may be made or used in the same way regardless of their position and orientation. Accordingly, it is to be understood that terms and phrases such as “under,” “upper”, “side,” “over”, “underneath”, “parallel”, “perpendicular”, “vertical”, etc., as used herein refer to relative location and orientation of various portions of the structures with respect to one another, and are not intended to suggest that any particular absolute orientation with respect to external objects is necessary or required.
The foregoing specification also describes processing steps. It is understood that the sequence of such steps may vary in different embodiments from the order that they were detailed in the foregoing specification. Consequently, the ordering of processing steps in the claims, unless specifically stated, for instance, by such adjectives as “before”, “ensuing”, “after”, etc., does not imply or necessitate a fixed order of step sequence.
Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature, or element, of any or all the claims.
Many modifications and variations of the present invention are possible in light of the above teachings, and could be apparent for those skilled in the art. The scope of the invention is defined by the appended claims.
