Technical Field

[0001] The present disclosure relates to a thin film X-ray diffraction sample cell device and method. In particular, the present invention relates to a thin film X-ray diffraction device for the measurement of material properties and structures during the application of electric fields.

Background of the Invention

[0002] The measurement of material structures using X-ray diffraction while the material is in an environment having an electric field can be used to determine information regarding the atomic and microstructural changes and their relationship to the properties of the material. This information may, in particular, be of interest to researchers considering electronic materials used for micro-electro-mechanical sensors and actuators. Electro mechanical materials, such as piezoelectrics, generate an electric charge in response to applied mechanical stress, and/or experience a mechanical strain in the presence of an electric field. Other material areas of interest include; ionic conductors, battery electrodes, thermoelectrics, and any other system where interaction of the electric field with the material has the potential to alter the material structure.

[0003] Currently commercial devices which may be used for the measurement of material structures using X-ray diffraction while the material is under an environment of electric field suffer from several drawbacks.

[0004] In order to obtain an understanding of the functional mechanisms of electro mechanical materials, it can be useful to measure diffraction patterns during the application of an electric field.

[0005] Many of the structural changes occurring in materials under the application of an electric field can be measured using diffraction. For example, X-ray diffraction and neutron diffraction offer a unique insight into the atomic and microstructural states of ferroelectric films. Among other structural changes, the technique has been used to characterise intrinsic lattice strains, measured as distortions to the unit cell, ferroelastic domain switching, measured as intensity changes between certain reflections, and also phase transformations, measured as unique diffraction signatures. [0006] Typically, researchers measure diffraction patterns using custom made devices and kits, which generally have a sample cell, to support the desired sample. The sample cell generally has two windows for the incident and scattered X-ray beams. There are various constraints and difficulties which apply to sample cell design such as:

The total thickness of the sample cell must be kept small for versatility to mount on different X-ray diffraction instruments;

It is important to minimise shadowing of the detector solid angle; and

It is necessary to isolate the electric current, for user safety and to avoid damage to the equipment.

[0007] Another problem with setting up such diffraction pattern measuring devices is that the sample is normally very small and it is difficult to mount the sample in a manner that permits it to be put in contact with the electric field and also allowing entrance and exit paths for X-ray scattering measurements.

[0008] Existing devices which are able to secure a sample in an electric field suffer from various drawbacks. For example, the geometry of the sample holding device is not suitable to be located within certain X-ray diffraction equipment. Furthermore, the devices generally do not permit the X-rays to be delivered through a wide angular range which may be required or at least desirable for testing.

[0009] Further drawbacks of existing X-ray diffraction measuring devices relate to both the field and temperature range over which they operate and their ability to simultaneously measure material properties.

[0010] A still further drawback concerning existing X-ray diffraction devices which are able to secure a sample in an electric field relates to their ease of use with respect to sample loading and unloading, which can be difficult due to the small size of the sample, and the need for the sample to be in contact with the electric potential, and held completely stationary during testing.

Object of the Invention

[0011] It is an object of the present invention to substantially overcome or at least ameliorate one or more of the above disadvantages, or to provide a useful alternative. Summary

[0012] In a first aspect, the present invention provides a thin film X-ray diffraction sample cell device comprising:

a body having a raised sample holder;

first and second probe tips located adjacent to the sample holder; and

first and second translation stages each operable to move one of said first and second probe tips relative to three generally perpendicular axes.

[0013] Each of the probe tips is preferably connected to an electric power supply.

[0014] The thin film X-ray diffraction sample cell device preferably comprises a cover configured to enclose the raised sample holder.

[0015] The cover preferably includes a partially spherical shield and upper and lower metallic annular members which clamp a circumferential flange of the shield in a rigid section, the rigid section being seated in an annular channel formed on an upper portion of the body.

[0016] The raised sample holder is preferably coupled to a heating element configured to increase the temperature of the raised sample holder.

[0017] A thermally insulated member is preferably located beneath the heating element.

[0018] The thin film X-ray diffraction sample cell device further preferably comprises a fan located in the body, within a heat sink.

[0019] A thermally conductive bridge preferably extends from beneath the thermally insulated member to the heat sink.

[0020] Each translation stage preferably includes:

a first mechanism configured to move one of the probe tips in a first direction, generally parallel to an upper surface of the raised sample holder;

a second mechanism configured to move said probe tip in a second direction, perpendicular to the first direction and generally parallel to an upper surface of the raised sample holder; and

a vertical height adjustment mechanism configured to vertically raise or lower said probe tip relative to the raised sample holder.

[0021] Preferably the first and second mechanisms are each controlled by wheels. [0022] The sample holder is preferably spring biased such that an upper surface of the sample holder remains stable when other components thermally expand.

[0023] The thin film X-ray diffraction sample cell device further preferably comprises a clamp configured to apply a force to an upper surface of a sample to prevent the sample from unintentional movement during X-ray diffraction.

[0024] The clamp is preferably spring biased.

[0025] An upper surface of the raised sample holder is preferably located above an uppermost surface of the body.

[0026] The probe tips are preferably in electric connection with a printed circuit board located within the body.

Brief Description of the Drawings

[0027] A preferred embodiment of the invention will now be described by way of specific example with reference to the accompanying drawings, in which:

[0028] Fig. 1 is a top perspective view of a thin film X-ray diffraction sample cell according to the invention;

[0029] Fig. 2 depicts the sample cell of Fig. 1 with the cover removed;

[0030] Fig. 3 is a first perspective cross-sectional view of the sample cell of Fig. 1;

[0031] Fig. 4 is a second perspective cross-sectional view of the sample cell of Fig. 1;

[0032] Fig. 5 is a third perspective cross-sectional view of the sample cell of Fig. 1;

[0033] Fig. 6 is a first cross-sectional side view of the sample cell of Fig. 1;

[0034] Fig. 7 is a second cross-sectional side view of the sample cell of Fig. 2;

[0035] Fig. 8 depicts a further embodiment of the thin film X-ray diffraction sample cell including a camera mount; and

[0036] Fig. 9 depicts the thin film X-ray diffraction sample cell of Fig. 1 in operation.

Detailed Description of the Preferred Embodiments

[0037] A thin film type X-ray diffraction sample cell device 100 is disclosed in Figures 1 to 9. The thin film sample cell device 100 enables an X-ray beam to be used for performing reflection type X-ray diffraction experiments on samples 50, whereby the X-ray beam is directed at a front surface of the sample 50. The X-ray beam may be applied through various angles around the circumference of the sample cell device 100. Furthermore, referring to Fig. 6, the X-ray beam may be applied at an angle of incidence ranging from 2 theta = 0 degrees to 180 degrees.

[0038] The thin film X-ray diffraction sample cell device 100 has a small form factor, which provides several advantages. Primarily, this enables the device 100 to have a geometry suitable for mounting on most laboratory based X-ray diffraction instrumentation. Furthermore, this small form factor enables the device 100 to be easily transported, and handled.

[0039] The thin film sample cell device 100 includes a housing body 110, fabricated from aluminium or another suitable material. The housing body 110 is defined by a housing body base member 120 and a housing body upper member 130 which is attached with screws or other suitable fasteners 140.

[0040] The fasteners 140 may be removed to separate the housing body upper member 130 and provide access to the internal components.

[0041] Referring to Fig. 1, the device 100 includes a removable cover 150. The cover 150 has a dome shaped portion 152 fabricated from Kapton™ film or another suitable polymer or material which is X-ray transmissible. A circumferential flange of the dome shaped portion 152 is clamped between upper and lower metallic annular members 154, 156 which clamp the Kapton film into a rigid section.

[0042] The cover 150 provides several functions. Firstly, it provides a physical safety shield to isolate the electric current from users. Secondly, the cover 150 provides thermal insulation, which assists to regulate the temperature in the vicinity of the sample 50 when X- ray diffraction is conducted at a temperature elevated above or lowered below the ambient temperature.

[0043] In the embodiment depicted in the drawings, the cover 150 is manually removable, and fitted to a recessed annular channel 160 formed in the housing body upper member 130. It will be appreciated that other engagement means may be deployed between the cover 150 and the housing body upper member 130.

[0044] Referring to Fig. 3, the housing body 110 includes one or more holes 170, or another suitable mounting formation, which permits the housing body 110 to be mounted on legs or another suitable support structure, plate or stand. In the embodiment depicted, screws 180 are mounted in the holes 170, and extend beyond the underside of the housing body 110. The screws 180 each have a head 190 which is accessible by a screw driver or other such drive tool.

[0045] Referring to Figs. 3 and 4, the thin film sample cell device 100 includes a sample support or holder 210. The sample support 210 is fabricated from a thermally conducting electrical insulator material, such as Aluminium Nitride.

[0046] The sample support 210 is seated within a thermally and electrically insulated housing 220 made for example from a ceramic material, such as MACOR.

[0047] The sample support 210 is spring mounted to the insulated housing 220.

Accordingly, the sample support 210 can be slightly displaced in a downward direction. This provides a mechanism to allow the sample 50 surface to roughly stay static when the components around the sample support 210 change temperature and thermally expand.

[0048] The thermally insulated member 205 in Fig. 3, located below the sample support 210, defines a thermal contact and electrical isolation, which in a preferred embodiment is fabricated from Macor. Insulated member 205 houses the heater elements and is in contact with the aluminium Nitride sample support 210. Member 205 is fabricated from Macor to minimize heat flow into the rest of the body.

[0049] Again referring to Fig. 3, a single multicore cable is connected to the housing body 110 through aperture 175. An internal printed circuit board (PCB) 112 is connected to the multicore cable. The circuit board 112 is electrically connected to a first probe tip 300, and a second probe tip 310. The printed circuit board (PCB) 112 is located in the cavity 410 for controlling the operation of the X-ray diffraction sample cell device 100.

[0050] Referring to Fig. 2, the device 100 includes two probe tips 300, 310. Each probe tip 300, 310 being selectively moveable by an independent translation station 305, 315, best seen in the cross-sectional view of Fig. 4. The probe tips 300, 310 can each be moved relative to three perpendicular axes, using three independent adjustment mechanisms, as discussed below.

[0051] Referring to Fig. 4, a first wheel 320 can be manually rotated to move the probe tip 300 laterally, in a direction radially inwardly or outwardly, relative to the sample 50. By winding the wheel 320, a threaded protrusion 330 moves relative to a corresponding internally threaded member 340. The result is that the threaded member 340 moves laterally, and an elongated arm 350 also translates the same distance. The probe 300 is connected to a distal end of the arm 350. As such, the probe tip 300 translates laterally by the same distance as the arm 350. In practice, the probe tip 300 can be moved around 5mm laterally. There are springs which push the arm 350 in the direction of the threaded member 340. In particular, on each translation station 305, 315 there are two channels 342 where springs are seated to push back. Fig. 4, shows the channels 342 in the Y direction. Similar channels are also present and act in the X direction.

[0052] A second wheel 400 is connected in a similar manner to the arm 350. The second wheel 400 is configured to move the arm 350 and hence the probe tip 300 in a

perpendicular direction, also being generally parallel with the upper surface of the sample 50, again around 5mm in total movement.

[0053] Again referring to Fig. 4, the vertical height of each probe tip 300, 310 can also be moved with a rotatable winder 500. By rotating the winder 500, the arm 350 pivots about a fulcrum 510. As such, rotating the winder 500 in a first direction causes the probe tip 300 to raise, and rotating the winder 500 in an opposing direction causes the probe tip 300 to lower.

[0054] Again referring to Fig. 4, section 355 moves with the arm 350 but keeps the air between the sample chamber area from mixing with the air in the general electronics and outside area.

[0055] The above described translation stages 305, 315 are extremely low profile in order to ensure the probe tip mechanisms can fit within the required maximum height of the device 100.

[0056] A similar translation stage 305, 315 is associated with each of the probe tips 300, 310, such that each probe tip 300, 310 can be moved in both X and Y directions, parallel to the surface of the sample 50 (see Fig. 4) and also vertically.

[0057] When a sample 50 is located on the sample support 210, the physical contact between the upper surface of the sample 50 and the probe tips 300, 310 closes the circuit, and allows the electric potential to be applied to the sample 50, thereby applying the electric field.

[0058] Referring to Fig. 2, a clamp 550 may be included in some embodiments. The clamp 550 is spring loaded or otherwise downwardly biased, and designed to apply a force to the upper surface of the sample 50 to prevent the sample 50 from unintentional movement during X-ray diffraction. [0059] With the exception of the probe tips 300, 310, the clamp 550, and the cover 150, the upper surface of the sample 50 when seated on the sample support 210 defines the uppermost portion of the device 100. This allows for the maximum possible range of X-ray scattering angles to be achieved during measurements.

[0060] Referring to Fig. 5, the thin film type X-ray diffraction sample cell device 100 includes a heating element which is seated in a cavity 600 located just below the sample support 210. The heating element 600 can be used to selectively raise the temperature from ambient temperatures up to about 300 degrees C. The heating element is associated with a heat sink 610 and electric fan 620 on account of a bridge of thermally conductive material 602.

[0061] The heat sink 610 and electric fan 620 enable the thin film type X-ray diffraction sample cell device 100 to maintain a desired temperature or temperature range at the sample support 210.

[0062] The operation of the thin film X-ray diffraction sample cell device 100 will now be described. An X-ray beam 350 is generated by a laboratory based X-ray instrument, or a synchrotron source and is directed through the cover 150. The incident beam is scattered and recorded against a detector, as depicted in Fig. 9, which records the sample diffraction pattern for a given electric field.

[0063] The electric field may be changed during the X-ray diffraction measurement to observe differing diffraction patterns. In practice, this may be achieved by varying the voltage applied to the probe tips 300, 310. The power source is variable and may be applied as an alternating current or a direct current.

[0064] In the first embodiment of the X-ray diffraction sample cell device 100, the voltage applied is typically up to magnitudes of +/- 50V.

[0065] Using the translation stages 305, 315, the positions of the two probe tips 300, 310 can be altered. This can be done along axes X, Y (Fig. 4) or alternatively the probe tips 300, 310 may be raised or lowered vertically.

[0066] In a further embodiment, the thin film sample cell device 100 includes a camera mount 400 that allows for placing of the probe tips 300, 310 accurately on specified sample locations. This enables positioning of the probe tips 300, 310 with micron precision.

[0067] In a further embodiment (not shown) the translation stages 305, 315 which control movement of the two probe tips 300, 310 may be automated and controlled by internal electric motors, such that adjustment of the location of the probe tips 300, 310 is controlled without direct user input, but rather is controlled by a computer system.

[0068] Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.