in order to grow high - quality epitaxial films of the “ high - pressure ” oxide phases described above , one needs to expose the sample during the growth (“ in - situ ”) to a high partial pressure ( say 0 . 1 - 10 bar ) of a gas such as molecular oxygen ( or ozone , atomic oxygen , no 2 , a mixture of two or more of these gases , or some other suitable gaseous source of oxygen ) and / or the high vapor pressure of one or more of volatile elements ( such as hg , tl , pb , bi , k , rb , etc .) on the other hand , for proper operation of the pld apparatus , it is necessary to keep the laser ablation target at a relatively low pressure ( say , 100 mtorr ). in order to simultaneously satisfy these two seemingly contradictory conditions , we have designed an apparatus described in what follows . a vacuum chamber suitable for pld is provided with one or more pumps ( such as a turbo - molecular pump or a cryo - pump provided with a backing mechanical pump ), a plurality of ports including optical windows , sample introduction port , feedthroughs for gas lines , water lines , and electrical connections , as well as mechanical supports for the heater assembly , the target , and the substrate holder . in one preferred embodiment , illustrated in fig1 the substrate holder is attached to a linear motion actuator , which moves the holder periodically between two fixed positions . in either position , the substrate holder serves as a top lid for the high - pressure heater sub - chamber , leaving only a very narrow opening ( typically less than 0 . 5 mm ) between the two . in one of the two positions , “ open ”, it is placed outside of this can , under a lower pressure , and facing the pld target and the laser - ablation plume . in this part of the film growth cycle , deposition occurs . in the other position , “ closed ”, the substrate is facing the high - pressure sub - chamber , and is consequently under a high pressure . in this part of the film growth cycle , the volatile gaseous species is loaded into the film . this could include oxidation of the more inert constituents , or incorporation of volatile elements such as hg , tl , pb , bi , k , rb , etc . this process resembles the one used by kinder et al [ 20 ] and by matijasevic and slycke [ 21 ] for deposition of large - area yba 2 cu 3 o 7 films . the key difference is that they use thermal co - evaporation and much lower pressure in both the deposition stage ( typically 10 − 5 torr ), and the oxidation stage ( typically 10 − 2 - 10 − 1 torr ). in contrast , we are using pld , and much ( 1 , 000 - 100 , 000 times ) higher pressure . with respect to incorporation of volatile cations , the process resembles somewhat the two - stage , ex - situ growth of thin films of tlbacacuo [ 11 ] and hgbacacuo [ 4 - 9 ], whereby certain precursor oxides are deposited first onto a substrate , and in the second stage , the sample is encapsulated and annealed under a high tl or hg pressure . however , in that case , the volatile cations have to diffuse through the entire film thickness , which is accompanied with a gross change of the bulk crystalline structure , and requires very high temperature and pressure . in consequence , the films re - crystallize and generally end up being polycrystalline , having very rough surfaces , and inferior transport properties . in the present case , in one deposition step , only a fraction ( typically between 0 . 01 and 0 . 5 ) of a molecular layer is deposited , and it is oxidized or loaded with the volatile cations immediately and before the deposition of the subsequent fraction of the molecular layer . in this way , oxidation or volatile cation loading occurs on a layer - by - layer basis . this obviates the need for gross bulk diffusion , permits film growth at reduced temperature , and provides for epitaxial growth , superior film morphology and physical properties . a further important aspect of the present invention is that for most of the duty cycle , i . e ., while it is in the “ closed ” position , the sample is effectively placed inside a black - body cavity , comprised of the high - pressure heater “ can ” and top lid or the “ cap ” 9 . this ensures good uniformity of the temperature over the entire substrate area . the linear motion actuator occasionally and periodically moves the substrate holder from “ closed ” position to the “ open ” position and back . generally , the duty cycle is low , say between 1 : 5 and 1 : 100 , so that the substrate spends most of the time in the “ closed ” position . the period is adjustable and typically can be about 1 hz , i . e ., the substrate typically goes “ open ” once per second . the laser action is synchronized with the linear motion actuator so that the laser is fired when the sample is in the “ open ” position . for example , if in one deposition event , 0 . 1 of a molecular layer of the desired compound is deposited , and the laser firing and substrate motion frequency is 1 hz , it will take 10 seconds for one molecular layer , or about 2 nm film thickness . in one minute , one would deposit 12 nm , and in one hour , 0 . 72 microns . in principle , it is possible to increase the deposition rate significantly , by increasing the frequency ( say to 10 hz ) and the laser energy density so that a larger fraction of a molecular layer is deposited in one burst . it is possible to further improve the apparatus described above by adding a second high - pressure sub - chamber , so that the substrate with the film is periodically switched between two closed positions , passing on its way from one to another through the “ open ” position . in this way , it is easier to implement a regime where the duty cycle is low , and the fraction of time in the “ open ” position the smallest , as the substrate is passing through this position at the maximum speed , and decelerates while it is in the “ closed ” position . in another preferred embodiment of the present invention , illustrated in fig2 the substrate is placed into a slot in the circular substrate holder , with an opening , so that most of the substrate &# 39 ; s bottom surface is exposed , and covered with a “ cap ”. the linear motion actuator is replaced by an ordinary motor , with which the substrate holder can be rotated continuously , above the high - pressure can . the latter does not comprise a full circle , but is terminated in such a way as to leave an opening that corresponds to the substrate size , through which the material can be deposited onto the substrate . thus , when the substrate holder is rotated , the substrate in effect switches between two positions , “ open ”, and “ closed ”. in either position , the substrate holder serves as a top lid for the high - pressure heater can , leaving only a very narrow opening ( typically less than 0 . 5 mm ) between the two . here also the duty cycle is low , say between 1 : 5 and 1 : 50 , so that the substrate spends most of the time in the “ closed ” position . the period is adjustable and typically can be about 1 hz , i . e ., the substrate typically goes “ open ” once per second . here , the frequency can be easily increased to 10 hz , which corresponds to 600 rpm of the motor , and even higher . the laser firing is synchronized with this , so that the ablation bursts coincide with the substrate being in the “ open ” position , i . e ., the ablated material is deposited onto the substrate . in yet another preferred embodiment of the present invention , the apparatus is further improved by using a two - stage differentially pumped linear - motion high - pressure heater assembly , as shown in fig3 . this apparatus is rather similar to the one shown in fig1 ; the new element here is the second , intermediary pressure sub - chamber , connected via a relatively large flange to the second pump . the opening between the top ( open ) side of this chamber and the substrate holder is a very narrow opening ( typically less than 0 . 5 mm ), so that in either the open or the closed position , or anywhere inbetween , the substrate holder serves as a top lid also for this intermediate - pressure sub - chamber . in this way , one can achieve a large degree of differential pumping , e . g ., about 100 mtorr in the main chamber , about 10 torr in the intermediate sub - chamber , and 0 . 1 - 10 bar in the high - pressure sub - chamber . significantly higher differential pumping ratios can also be obtained in this way . the same improvement , i . e ., adding a second differential - pumping stage , is also possible in the circular motion geometry as described above , and is included in the present invention as yet another preferred embodiment . critical to the proper functioning of the present apparatus , i . e ., to achieving of a high differential pumping ratio , is to ensure a tight fit , i . e ., a small distance between the two surfaces , of the substrate holder on one side and of one or two higher - pressure vessels , on the other . this is somewhat difficult because this tight fit must be achieved during the operation under high temperatures ( say 500 - 1 , 000 ° c .). other then precise machining , here we can employ one or more of the following improvements . first , one can allow the substrate holder to actually touch the high - pressure can under normal atmosphere , and let it move out by the pressure and gas flow , once the chamber is evacuated , under the bending force provided by the pressure difference . this bending force should be nearly offset by the substrate holder weight and the elastic force , so that the resultant opening is small and controllable . another possible improvement is to insert one or several cylindrical rollers between the substrate holder and the high - pressure can &# 39 ; s surface , so that the substrate holder lays on these rollers . in this way , the opening between the substrate holder and the high - pressure chamber would be minuscule . this would allow for even higher differential pressure ratio , even with just a single stage apparatus . based on the teachings herein , it would be apparent to one of ordinary skill in the art that it is possible to invert all of the above structures upside - down , or even to place them at arbitrary angles . the present invention includes all such variations . one advantage of the geometry shown here is that one could easily place inside the high - pressure heaters a vessel containing liquid or powder of the desired volatile atomic species , instead of or in addition to supplying the gasses through the high - pressure gas inlets . the above embodiments of the present invention all assume using a standard ( say , tungsten or nickel - chrome ) wire or tape heater , generally providing the temperature which is not only uniform across the sample but also constant in time during the film growth . however , in another embodiment of the present invention we can instead use a powerful lamp heater which can be ramped up and down very fast , generating flashes of heat directed at the sample . this resembles somewhat rapid thermal annealing ( rta ) process used currently in semiconductor industry . a laser heater could also be used for the same purpose . in this way , one can separate the film deposition process into two stages . first , one deposits the precursor material , which does not contain the volatile component , onto a cold substrate , say at or close to the room temperature . this will be amorphous in general . next , one transfers the sample to the high - pressure chamber , where the sample is simultaneously exposed to a high pressure of the volatile species and to rta . this should both induce incorporation of the volatile species and re crystallization of the film . the film is then cooled down to or near to the room temperature , and only then transferred to the “ open ” position , for deposition of another increment of the material . in this way , one ensures that there is no decomposition of the material , nor escape of the volatile species , while it is in the “ open ” position . again , an important novel feature here is that this process of precursor deposition / rta plus loading with the volatile species occurs on a molecular layer basis , or even for a fraction of such layer at a time . this should ensure good epitaxy , smooth film surface , and superior transport and other physical properties . as a further improvement of the present invention , it is possible to lower the substrate holder ( or rise the high - pressure can ) once the substrate is brought to the “ closed ” position , to seal the opening between the two . this would enable flushing the gas also in bursts , with the highest pressure being achieved when the sample is in the “ closed ” position . in this way , it is possible to further increase the difference in the pressure between the “ open ” and the “ closed ” sample positions . as a further improvement of the present invention , instead of the molecular oxygen , it is possible to use ozone , atomic oxygen , oxygen plasma , no 2 , or some other stronger oxidant , or any mixture of two or more of these gases . referring now more specifically to fig1 a pulsed laser deposition ( pld ) system with a single - stage , linear - motion , high - pressure heater assembly is illustrated . a vacuum chamber 1 is provided with a pump 2 ( such as a turbo - molecular pump provided with a backing mechanical pump ), a plurality of flanges carrying optical windows , sample introduction port , feedthroughs for gas lines , water lines , and electrical connections , as well as mechanical supports for the high - pressure heater assembly 3 , the target 4 , and the linear motion actuator 5 . the substrate 6 is placed into a slot 7 in the substrate holder 8 , with an opening , so that most of the substrate &# 39 ; s bottom surface is exposed , and a top cover or “ cap ” 9 . the substrate holder 8 can be moved between two positions , position 10 or “ open ”, and position 11 or “ closed ”, by means of the linear motion actuator 5 . in either position , the substrate holder 8 serves as a top lid for the high - pressure heater sub - chamber 3 , leaving only a very narrow opening ( typically less than 0 . 5 mm ) between the two . the high - pressure sub - chamber 3 is further provided with a heater 12 , possibly a removable shield 13 of good thermal conductivity and inert to the chemicals involved , a water - cooling assembly 14 , one or more gas inlets 15 , and possibly a temperature sensor 16 such as a thermocouple . to connect these , the chamber 1 is provided with one or more feedthroughs 17 for the electrical connections for the heater 12 , the water lines 14 , the gas lines 15 , and the thermocouple 16 . by the virtue of this construction , including the “ cap ” 9 , in the “ closed ” position 11 , the substrate is essentially enclosed in a black - body cavity . this ensures good uniformity of the temperature . the linear motion actuator occasionally and periodically moves the substrate holder 8 from the “ closed ” position 11 to the “ open ” position 10 and back . generally , the duty cycle is low , say between 1 : 10 and 1 : 100 , so that the substrate spends most of the time in the “ closed ” position 11 . the period is adjustable and typically can be about 1 hz , i . e ., the substrate typically goes “ open ” once per second . the laser firing is synchronized with this , so that the ablation bursts coincide with the substrate being in the “ open ” position , i . e ., the ablated material is deposited onto the substrate . the light beam from a laser 18 is focused , by means of a lens 19 , through an optical port 20 , onto the target 4 . the latter can be a pressed - ceramic target , or a single crystal , of the desired composition . the laser 18 can be an excimer laser , or some other laser with enough power to cause ablation of the target , and generate a plume 21 . the direction of the light beam and the orientation of the target 4 can be adjusted so that the plume 21 is aimed at the substrate 6 when the latter is in the “ open ” position 10 . referring now more specifically to fig2 a single - stage , circular - motion , high - pressure heater assembly is illustrated . here , substrate 6 is placed into a slot 7 in a circular substrate holder , with an opening , so that most of the substrate &# 39 ; s bottom surface is exposed , and covered with “ cap ” 9 . the circular substrate holder can be rotated continuously , above the high - pressure can . the latter does not comprise a full circle , but is terminated in such a way as to leave an opening that corresponds to the substrate size , through which the material can be deposited onto the substrate . thus , when the circular substrate holder is rotated , the substrate 6 in effect also switches between two positions : an “ open ” position where it is outside the high - pressure can and a “ closed ” position where it is facing the high - pressure sub - chamber and is consequently exposed to a high pressure . in either position , the substrate holder serves as a top lid for the high - pressure heater can , leaving only a very narrow opening ( typically less than 0 . 5 mm ) between the two . the high - pressure sub - chamber or can is further provided with a heater , a removable shield 13 of good thermal conductivity and inert to the chemicals involved , one or more gas inlets , a water - cooling assembly ( not shown ), a temperature sensor such as a thermocouple ( not shown ), etc . this high - pressure sub - chamber is placed inside a vacuum chamber provided with pumps , viewports , feedthroughs , target holder , etc . ( not shown ). an excimer laser or another powerful laser ( not shown ) is used to ablate the target and deposit the film onto the substrate , as in fig1 . here also the duty cycle is low , say between 1 : 5 and 1 : 50 , so that the substrate spends most of the time in the “ closed ” position . the period is adjustable and typically can be about 1 hz , i . e ., the substrate typically goes “ open ” once per second . the laser firing is synchronized with this , so that the ablation bursts coincide with the substrate being in the “ open ” position , i . e ., the ablated material is deposited onto the substrate . referring now more specifically to fig3 a pulsed laser deposition ( pld ) system with a two - stage differentially pumped linear - motion high - pressure heater assembly is illustrated . this apparatus is rather similar to the one shown in fig1 except that here we have added a second differential pumping stage . vacuum chamber 1 is provided with pump 2 , a plurality of flanges carrying optical windows , sample introduction port , feedthroughs for gas lines , water lines , and electrical connections , as well as mechanical supports for high - pressure heater assembly 3 , target 4 , and linear motion actuator 5 . substrate 6 is placed into slot 7 in substrate holder 8 , with an opening , so that most of the substrate &# 39 ; s bottom surface is exposed , and the top cover or “ cap ” 9 . substrate holder 7 can be moved between the “ open ” and “ closed ” positions by means of linear motion actuator 5 , as in fig1 . in either position , substrate holder 8 serves as a top lid for high - pressure heater sub - chamber 3 , leaving only a very narrow opening ( typically less than 0 . 5 mm ) between the two . high - pressure sub - chamber 3 is further provided with a heater 12 , a removable shield 13 of good thermal conductivity and inert to the chemicals involved , a gas inlet 15 , a water - cooling assembly ( not shown ), and a thermocouple ( not shown ). to connect these , chamber 1 is provided with one or more feedthroughs for the electrical connections for heater 12 , gas lines 15 , the water lines , and the thermocouple . the new element here is the second , intermediary pressure sub - chamber 22 , connected via a relatively large tube end flange to the second pump 23 . the opening between the top ( open ) side of this sub - chamber and substrate holder 8 , is very narrow ( typically less than 0 . 5 mm ), so that in either the “ open ” or the “ closed ” position , or anywhere in - between , substrate holder 8 also serves as a top lid for this intermediate - pressure sub - chamber 22 . in this way , one can achieve a large degree of differential pumping , e . g ., ca . 100 mtorr in the main chamber , ca . 10 torr in the intermediate sub - chamber , and ca . 1 , 000 torr in the high - pressure sub - chamber . like in fig1 in the “ closed ” position , the substrate here is essentially enclosed in a black - body cavity , which ensures good uniformity of the temperature . the linear motion actuator occasionally and periodically moves substrate holder 8 from the “ closed ” position to the “ open ” position and back . generally , the duty cycle is low , say between 1 : 10 and 1 : 100 , so that the substrate spends most of the time in the “ closed ” position 11 . the period is adjustable and typically can be about 1 hz , i . e ., the substrate typically goes “ open ” once per second . the laser firing is synchronized with this , so that the ablation bursts coincide with the substrate being in the “ open ” position , i . e ., the ablated material is deposited onto the substrate . like in fig1 the light beam from a laser 18 is focused , by means of a lens 19 , through an optical port 20 , onto the target 4 . the later can be a pressed - ceramic target , or a single crystal , of the desired composition . the laser 18 is an excimer laser , or some other laser with enough power to cause ablation of the target , and generate a plume 21 . the direction of the light beam and the orientation of the target 4 can be adjusted so that the plume 21 is aimed at the substrate 6 when the latter is in the “ open ” position .