Temperature dependence of the penetration depth in YBa2Cu3O7-delta measured by microwave ring resonators

YBa2Cu3O7-(TM) (YBCO)) superconducting ring resonators with a YBCO ground p lane were fabricated using double-side YBCO films deposited on LaAlO3 (LAO) substrates. The temperature dependent London penetration depth, Delta lamb da = lambda (T)-lambda (5K), was systematically studied by varying the oxyg en content of the same resonator structure. For fully oxygenated condition (delta = 0.05), the resonator exhibits a quality factor Q > 10(4) at 16K, a nd Delta lambda (T) displays a linear behavior over a wide range of tempera tures. With increasing delta (e.g. delta = 0.2), although Delta lambda is s till linear in temperature, the slope changes by more than a factor of 2. A s delta is further increased, Delta lambda (T) changes fi om T- to T-2-depe ndence. The results suggest that in the underdoped regime, the incoherent s cattering of charged carriers may become increasingly prominent.