TY - JOUR
T1 - Carrier-tuning of single-crystalline Ba8Ga16Ge30
AU - Avila, M. A.
AU - Suekuni, K.
AU - Umeo, K.
AU - Takabatake, T.
N1 - Funding Information:
We are thankful to Y. Shibata for the EPMA analysis. The low-temperature measurements were performed at the Materials Science Center, N-BARD, Hiroshima University. This work was supported by a Grant-in-Aid for Scientific Research (COE Research 13CE2002) of MEXT, Japan.
PY - 2006/8/15
Y1 - 2006/8/15
N2 - Despite the fact that the only practical route to self-flux single crystal growth of Ba8Ga16Ge30 clathrates is through excess Ga flux, we have developed a method which results in p-type or n-type samples, depending on the relative Ge content in the starting mixture, and thus allows us to gain effective control over the charge carrier nature and density. An initial Ba:Ga:Ge ratio of 8:38:30 results in p-type crystals with average composition Ba8Ga16.6Ge29.4, while those grown from 8:38:34 initial ratio are n-type with average composition Ba8Ga15.9Ge30.1. More importantly, the thermopower S(T), resistivity ρ(T) and thermal conductivity κ(T) show radically different behaviors. The p-type crystals show: (i) monotonically increasing S(T) up to S(300 K)≈+200 μV/K, (ii) semiconducting ρ(T) (which decreases two orders of magnitude between 10 and 300 K), and (iii) a glass-like low-temperature plateau in κ(T). In contrast, the n-type crystals show: (i) monotonically decreasing S(T) down to S(300 K)≈-200 μV/K, (ii) metallic ρ(T) in the 1-3 mΩ cm range, and (iii) a low-temperature crystalline peak in κ(T).
AB - Despite the fact that the only practical route to self-flux single crystal growth of Ba8Ga16Ge30 clathrates is through excess Ga flux, we have developed a method which results in p-type or n-type samples, depending on the relative Ge content in the starting mixture, and thus allows us to gain effective control over the charge carrier nature and density. An initial Ba:Ga:Ge ratio of 8:38:30 results in p-type crystals with average composition Ba8Ga16.6Ge29.4, while those grown from 8:38:34 initial ratio are n-type with average composition Ba8Ga15.9Ge30.1. More importantly, the thermopower S(T), resistivity ρ(T) and thermal conductivity κ(T) show radically different behaviors. The p-type crystals show: (i) monotonically increasing S(T) up to S(300 K)≈+200 μV/K, (ii) semiconducting ρ(T) (which decreases two orders of magnitude between 10 and 300 K), and (iii) a glass-like low-temperature plateau in κ(T). In contrast, the n-type crystals show: (i) monotonically decreasing S(T) down to S(300 K)≈-200 μV/K, (ii) metallic ρ(T) in the 1-3 mΩ cm range, and (iii) a low-temperature crystalline peak in κ(T).
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U2 - 10.1016/j.physb.2006.03.074
DO - 10.1016/j.physb.2006.03.074
M3 - Article
AN - SCOPUS:33746518592
VL - 383
SP - 124
EP - 125
JO - Physica B: Condensed Matter
JF - Physica B: Condensed Matter
SN - 0921-4526
IS - 1
ER -