17  EP 2 000 008 B1 18  substrate transport mechanism ( 60, 360), in- cluding: a plurality of first turning guides ( 64,  164, 364) spaced apart along the first precursor zone, at least some of the first turn guides adapted to support the substrat e during a change in a direction of travel of the substrate toward the second precursor zone, and apluralityofsecond turningguides( 66, 166, 366) spaced apart along the secondprecur- sor zone, at least some of the second turn- ingguidesadapted tosupport the substrate during a change in a direction of travel of the substrate toward the first prec urso zone. introducing a first precursor gas into a first pre- cursor zone (14, 114, 314); introducing a second precursor gas into a sec- ond precursor zone (16, 116, 316) spaced apart from the first precursor zone, the second pre- cursor gasbeing different fromthe first precursor gas; guiding a flexible substrate (12, 112, 312) back and forthbetween the first and secondprecursor zones and through a series of flow-restricting passageways (54, 56, 154, 156, 354, 356)of an a third precursor zone (190) separated from the firstand secondprecursor zonesandintowhich a third precursor gas different from the first and second precursor gases is introduced when the system is in use; a series of third passageways (192) extending through the third divider and into the third pre- cursor zone from the isolation zone, the third a third divider separating the third precurso zone from the isolation zone; and a payout spool (72, 172, 372) for paying out the substrate from a coil (74, 174, 374) for receipt at a first end (76, 376) of the isolation zone; and a take-up spool (74, 174, 374) for coiling the substrate received from a second end (84, 384) of the isolation zone opposite the first end. an exhaust line (440) connected to one or more of the precursor zones; and a precursor trap (59, 410, 420) located in the exhaust line. a first precursor delivery system (24, 124, 324) coupled to the first precursor zone for supplying the first precursor gas tothe first precursor zone; a second precursor delivery system ( 26, 126, 326) coupled to the second precursor zone for supplying the second precursor gas to the sec- ond precursor zone; and an inert gasdeliverysystem ( 28, 128, 328) cou- pled to the isolation zone for injecting an inert gas intotheisolation zone toachievea pressure in the isolation zone that is greater than pres- sures within the precursor zones. passageways spaced apart along the third pre- cursor zone and arranged for the substrate to be threaded therethrough back and forth be- tween the secondand thirdprecursor zonesand through the isolation zone. 6. The system of anyprecedingclaim, further compris- ing: 2. The system of claim 1, further comprising a first di- vider (34, 134, 334) separating the isolation zone from the first precursor zone, and a second divider (36, 136, 336) separating theisolation zonefromthe second precursor zone, and in which the flow- re- stricting passageways includes a series of first pas- sageways(54, 154, 354) through the first divider and a series of second passageways ( 56, 156, 356) through the second divider. 3. The system of claim 1 or 2, in which at least some of the first turning guides are adjustably mounted within the first precursor zone for movement toward and away from the isolation zone, to thereby adjust a dwell time of the substrate in the first precursor zone. 4. The systemofanypreceding claim,inwhich the sub- strate transport mechanism further comprises: 5. The system of any preceding claims, further com- prising: 7. The systemof any preceding claim,in whichat least some of the passageways include a tunnel. 8. The system of any precedingclaim, further compris- ing: 9. The system of claim 8, furthercomprisingarecycling line (450) connected between theprecursor trap and one or more of the precursor zones. 10. The system of anyprecedingclaim, further compris- ing a radicals generator for supplying a precursor radical to one or more of the precursor zones. 11. The systemof any preceding claim,in whichat least some of the turning guides include a heated roller. 12. A method for depositing a thin film on a flexible sub- strate (12, 112, 312), comprising: 10