Patent Application
20090151434
This invention relates to using a slider as a probe in an atomic force microscope and/or the use of a Peltier plate to control the temperature of a test surface in an atomic force microscope.
Atomic force microscopes have been in use for several years in analyzing some material properties of disks used in hard disk drives, such as friction/adhesion force on disk surfaces. Typically, these microscopes use a cantilever positioning a probe often made of Si3N4 with a silicon doped tip coated with aluminum or gold when measuring the surface energy. While these measurements were an improvement over the past, they do not adequately reveal what would happen if the same surface is used with a slider in a disk drive, because probes and sliders are made of fundamentally different materials and do not interact the same with the surface.
Another problem with atomic force microscopes is that they require an expensive temperature control stage to control the temperature of surfaces being tested. A new, less expensive temperature control mechanism would be very useful.
One embodiment of the invention includes an Atomic Force Microscope (AFM) with a test stand for a test object including a test surface and a positioning mechanism for a cantilevered probe including a cantilever coupled to a slider used in a disk drive. The disk drive may be a ferromagnetic and/or a ferroelectric disk drive.
The test surface may be composed as a disk surface in the disk drive. The slider positioned over the test surface creates a friction-adhesion measurement to estimate the friction-adhesion of the slider over a disk surface, and/or a lubricant depletion measurement to estimate the lubricant depletion, and/or a scratch test measurement to estimate a scratch test of the slider on the disk surface in the disk drive.
The cantilevered probe preferably includes a cantilever coupled to a slider useable in a disk drive, where the cantilever is configured for AFM use.
The AFM may include a Peltier plate configured to thermally couple to a test object to create the test surface at a controlled test temperature and may be used to refine the above-mentioned estimates to account for the controlled test temperature in the disk surface. The Peltier plate may be used with cantilevered probes that do not include a slider.
This invention relates to using a slider, such as those generally found in or otherwise useable in a disk drive, in an atomic force microscope, instead of a probe typically used in an atomic force microscope. The invention also relates to the use of a Peltier plate to control the temperature of a test surface in an atomic force microscope.
Referring to the drawings more particularly by reference numbers,
As used herein, the term Atomic Force Microscope (AFM) 10 will refer to a scanning probe microscope using a positioning mechanism 6 coupled through a cantilever 22 to a probe to measure at least one physical property of a test surface 4 of a test object 2. Often the physical properties are measured by observing the deflection of the cantilever. In some circumstances, the resistance, voltage drop, and/or current between the probe and a second terminal may also be measured.
A control circuit 48 may operate the AFM 10 to use the cantilevered probe 20 with the slider 24 positioned over the test surface 4 composed as a disk surface 62 to create a friction-adhesion measurement 32 to estimate the friction-adhesion of the disk slider 24 over the disk surface 62 in the disk drive 60, to create a lubricant depletion measurement 34 to estimate the lubricant depletion of the disk slider over the disk surface, and/or to create a scratch test measurement 36 to estimate the scratch test of the slider on the disk surface.
The test surface 4 may preferably be composed of material for use as a disk surface 62 in the disk drive 60. The disk drive may be a ferromagnetic disk drive as shown in
Another embodiment of the invention involves a cantilevered probe 20 including a cantilever 22 coupled to a slider 24 of a kind used in a disk drive 60, and the cantilever is configured for use in an AFM 10. The cantilevered probe may further include a vertical micro-actuator 26 coupled to the slider and at least one vertical control signal 28 provided to the vertical micro-actuator to alter a height 30 of the slider over the test surface 4. The vertical micro-actuator may further be included in the slider. As used herein a vertical micro actuator preferably refers to at least one heating element near read-write head which may include writers and readers.
In certain embodiments, the AFM 10 may include a Peltier plate 50, mounted on the test stand 8, configured to thermally coupled to the test object 2 to bring the test surface 4 to a controlled test temperature 52. The AFM may or may not use the cantilevered probe including a slider when using the Peltier plate.
Preferably, the Peltier plate 50 is thermally coupled to the test object 2 and operated to maintain the test surface 4 at the controlled test temperature 52. This supports refining the above-mentioned measurements 32, 34 and 36 to estimate those conditions at controlled test temperatures in the disk drive 60. An atmospheric chamber 70 shown in
While in general the slider 24 may be coupled to a vertical micro-actuator 26, in many embodiments, it will be preferred that the slider include a heater as shown in
The air bearing operates with the vertical micro-actuator 26 bringing the read-write head within the flying height off of the disk surface 62. The flying height is now frequently less than 10 nanometers (nm) and recently it has been found that under certain conditions of air temperature 40, humidity 38 and air speed 42, condensation can form dropping the pressure in the air bearing and potentially leading to crashing the slider into the disk surface. These conditions can be estimated with a refinement of the AFM 10 as shown in
Using a slider 24 for a ferroelectric disk drive 60, the AFM 10 may be used to generate a contact pressure measurement 47 to estimate the contact pressure within the ferroelectric disk drive.
The control circuit 48 may preferably include at least one instance of a controller 80 including at least one computer 84 operating the AFM 10 and/or operating the Peltier plate 50 as instructed by a program system 90. The program system includes program steps residing in the memory 82 accessibly coupled via a bus 86 to the computer. Each controller as used herein receives at least one input, updates and maintains at least one state, and generates at least one output based upon the value of at least one of the inputs and/or at least one of the states. A controller may also include a finite state machine and/or a neural network and/or an inferential engine.
The computer 84 may include at least one data processor and at least one instruction processor instructed by the program system to at least partly operate the AFM 10 and/or the Peltier plate 50 as disclosed herein. Each of the data processors may be instructed by at least one of the instruction processors.
Note that the program steps included in the program system 90 may represent the actions of various states of the finite state machine. The memory 82 may include a non-volatile memory component and/or a volatile memory component. As used herein, a non-volatile memory component retains its memory state without required power and a volatile memory component tends to lose its memory state without at least occasionally being supplied power.
The resistive probe in the slider 24 may use the electrode path 80 to create a circuit between the electrode sheet and the resistive probe contacting the disk surface 62 at a probe site to access a ferroelectric cell. The ferroelectric cell may be formed between the resistive probe site on the resistive probe surface, the ferroelectric film between the resistive probe surface and the electrode sheet through the electrode path.
The electrode sheet may be deposited on a disk substrate. The disk substrate may include a glass disk substrate and/or a metallic disk substrate similar to those used in contemporary ferromagnetic disks for hard disk drives. The electrode sheet may include at least one conductive metal. For the purpose of clarity, the application will speak of the electrode sheet and the disk substrate as distinct, however there may be embodiments where they are essentially the same.
The ferroelectric film may include a concentration, essentially consisting of the group of elements in a mixture: lead (Pb), zirconium (Z), titanium (Ti), and oxygen (O). These elements may further form a compound, and the ferroelectric film may preferably include the Pb(Zr0.4Ti0.6)O3 compound. The concentration may preferably be at least ninety percent of the molecular weight of the ferroelectric film.
The disk surface 62 and similarly the test surface 4 may preferably include a layer of Diamond Like Carbon (DLC) topped by a layer of lubricant. The resistive probe preferably contacts the lubricant layer without penetrating it, thereby avoiding solid-to-solid contact with the DLC layer. The DLC layer may be manufactured by high energy deposition of carbon on the ferroelectric film. The lubricant layer may include at least one lubricant compound from the perfluoropolyether family.
Reading the ferroelectric cell in the ferroelectric disk drive 60 uses the electrode path 80 to electrically couple the electrode sheet to the resistive probe to detect a sensed current between the resistive probe and the electrode sheet.
The preceding embodiments provide examples of the invention and are not meant to constrain the scope of the following claims.
