Laser-induced Thermoelectric Voltage Research Articles

Preparation and Laser-Induced Thermoelectric Voltage Effect of Bi2Sr2Co2Oy Thin Films Grown on Al2O3 (0001) Substrate.

Bi2Sr2Co2Oy thin films were grown on 10° vicinal-cut Al2O3 (0001) single crystalline substrates by pulsed laser-deposition techniques with in situ annealing, post-annealing and non-annealing process, respectively. The pure phase Bi2Sr2Co2Oy thin film was obtained with a non-annealing process. The result of X-ray diffraction showed that Bi2Sr2Co2Oy thin film was obviously c-axis preferred orientation. The laser-induced thermoelectric voltage signals were detected in Bi2Sr2Co2Oy thin films, which originated from the anisotropy of the Seebeck coefficient. The maximum peak value of laser-induced thermoelectric voltage was strong and could reach as large as 0.44 V and the response time was 1.07 μs when the deposition time was 6 min. Furthermore, the peak voltage enhanced linearly with the single-pulse laser energy. These characteristics demonstrate that Bi2Sr2Co2Oy thin film is also an excellent choice for laser energy/power detectors.

Laser-induced transverse voltage effect in c-axis inclined CuCr0.98Mg0.02O2 thin films with dominant phonon thermal conductivity

CuCr1−xMgxO2 (x = 0 and 0.02) epitaxial thin films were prepared on 5°/10° vicinal cut α-Al2O3 (000l) substrates using pulsed laser deposition. The laser-induced thermoelectric voltage (LITV) effect in these inclined delafossite thin films was observed for the first time. The thin films were characterized by resistivity temperature measurement and atomic force microscopy. Because of the enhanced resistivity anisotropy and high carrier concentration in the ab-plane owing to Mg doping, the 10°-tilted CuCr0.98Mg0.02O2 film exhibits an evident LITV signal with a maximum transverse thermoelectric voltage of 156 mV. Thermal conductivity results indicate that CuCr1−xMgxO2 (x = 0 and 0.02) films have a dominant phonon thermal conductivity, which may contribute to a long decay time for the LITV signal. These results indicate potential for future transverse thermoelectric applications based on transparent conductive oxides.

Doping dependence of laser-induced transverse thermoelectric voltages in the perovskite Nd2−x Ce x CuO4 thin films

Large laser-induced thermoelectric voltages (LITVs) are measured in the electron-doped Nd2−x Ce x CuO4 thin films grown on the vicinal-cut SrTiO3 substrates by pulsed laser deposition. The dependence of LITV signals upon the doping carrier density is investigated by changing the Ce content of the films. The optimum Ce dopant corresponding to the largest voltage is found and is attributed to the two-dimensional transport behaviors of the localized electrons. The shorter laser irradiation always induces the larger voltage signals in samples with richer Ce content, suggesting the optimum dopant level is sensitive to the wavelength of excitation source. Thus, the behaviors of LITV signals are resulted from both effects of the anisotropic thermoelectric transport and the optical properties of the thin films. The doping dependence related with an anisotropic charge transport may come from the change in carrier density and the modification in energy band configuration.

Laser-induced thermoelectric voltage effect of La0.9Sr0.1NiO3 films

Laser-induced thermoelectric voltage effect signal was observed in the La0.9Sr0.1NiO3 (LSNO) thin films grown on LaAlO3 single crystal substrate which is cut with 5° tilting angle along the 〈100〉 direction by excimer pulsed laser deposition. The results of the LITV measurement demonstrated that the peak voltage of LSNO thin films was strong and could reach as large as 700mV when laser energy density is 2mJ/mm2. The rising time of LITV signal was less than 20ns. Moreover, the peak voltage increased linearly with the single-pulse laser energy density. Above characteristics indicate LSNO thin films are a potential candidate for laser energy/power detectors is an excellent choice.

A novel strongly correlated electronic thin-film laser energy/power meter based on anisotropic Seebeck effect

Strongly correlated electronic (SCE) materials including high-temperature superconducting cuprate and colossal magnetoresistance manganite thin films demonstrate tremendous anisotropic Seebeck effect which makes them very promising for developing high-performance laser detectors. In this work, laser-induced thermoelectric voltage (LITV) signals with nanosecond response time have been measured in SCE La1−x Pb x MnO3 thin films based on anisotropic Seebeck effect at room temperature. The magnitude of the LITV signals increases linearly with laser energy/power density in a wide range of laser wavelengths from ultraviolet, visible to infrared based on which a novel SCE thin-film laser energy/power meter has been developed.

Laser-induced thermoelectric voltage in La0.9Pr0.1MnO3 thin films

The laser-induced thermoelectric voltage (LITV) was observed in La0.9Pr0.1MnO3 thin films grown on the vicinal cut LaAlO3 substrate by pulsed laser deposition for the first time. The detected signals were demonstrated to be originated from the anisotropic Seebeck effect. The largest peak value of the voltage is about 2.4 V, the full width at half-maximum of the temporal voltage peak and the rising time are 300–500 and 40–50 ns, respectively. It is a high quality and efficient material in the LITV family.

A high-performance laser energy meter based on anisotropic Seebeck effect in a strongly correlated electronic thin film

We have developed a high-performance laser energy meter based on anisotropic Seebeck effect in a strongly correlated electronic (SCE) thin film. SCE thin films, typically represented by high-temperature superconductor (HTS) cuprate and colossal magnetoresistance (CMR) manganite thin films, demonstrate tremendous anisotropic Seebeck effect. In this study, a La2/3Ca1/3MnO3 thin film grown on a tilted LaAlO3 substrate is tested with the fundamental, the second, the third, and the fourth harmonics (1064, 532, 355, 266 nm, respectively) of a Q-switched Nd:YAG laser over a wide range of temperatures from room temperature to 16 K. The peak-value of the laser-induced thermoelectric voltage signal shows a good linear relationship with the laser energy per pulse in the measured wavelength and temperature ranges. The combined advantages over other commercial laser detectors such as nanosecond-order response and spectrally broad and flat response over a wide range of temperatures, in situ real-time measurement, and energy savings, make the device an ideal candidate for next-generation laser detectors and laser power/energy meters.

Influence of Ca Content on LITV Effect of La<sub>1-x</sub>Ca<sub>x</sub>MnO<sub>3</sub> Epitaxial Thin Films

La1-xCaxMnO3 (x=0.0-1.0) epitaxial thin films were deposited on both tilted and untilted LaAlO3 (0 0 1) single crystalline substrates using PLD (pulsed laser deposition) technique, in which the employed qualified polycrystalline La1-xCaxMnO3 targets were synthesized by sol-gel method. The structural properties and the ultraviolet LITV (laser induced thermoelectric voltage) effect of the as-grown films on the tilted substrates were studied. The results demonstrate that the intensities of the LITV signals depend non-monotonously on Ca content, that is, the peak values of the LITV signals firstly increase and then decrease with Ca content increasing. The maximal peak value of LITV was found in the film with Ca=0.33.

Laser Induced Thermoelectric Voltage Effect of LaNiO<sub>3</sub>/LaAlO<sub>3</sub> Multilayer

LaNiO3 single layer, LaNiO3/LaAlO3 superlattice on vicinal-cut single crystalline LaAlO3 (100) and LSAT (100) substrates were prepared by pulsed laser deposition technique. Single-phased LaNiO3 polycrystal target, which is synthesized by sol-gel method, is employed in the thin film deposition process. The structure and physical properties of both the targets and thin films are analyzed. X-ray diffraction results show LaNiO3 single layer is of c-orientation and textural growth, therefore LaNiO3/LaAlO3 forms not superlattice but multilayer. The ultra-violet LITV (laser induced thermoelectric voltage) effects of the LaNiO3/LaAlO3 mutilayer and LaNiO3 single layer were investigated. A comparison study of the influence of LaNiO3 targets prepared by different sol-gel method on the physical property, and LITV effect of thin films was performed as well.

The Fabrication of La<sub>0.9</sub>Sr<sub>0.1</sub>CoO<sub>3</sub> Thin Films and its LITV Effect Applications

High quality La0.9Sr0.1CoO3 (LSCO) thin films grown on 5° vicinal cut LaAlO3 (LAO) (100) substrates were deposited by pulse laser deposition (PLD). Laser induced thermoelectric voltage (LITV) was detected instantly with fast response time and extremely narrow full width at half maximum (FWHM) when 248 nm pulse laser radiated on the surface of LSCO thin films. These merits of LSCO thin films make it one ideal material to fabricate light detectors and photosensitive device. With the increase of pulse laser energy, the peak voltages increase linearly, so LSCO thin films can be used to make high precision laser energy/power meter.

Time-integral type strongly correlated electronic thin-film laser energy meter

Strongly correlated electronic (SCE) systems, such as high-temperature superconducting (HTSC) cuprate and colossal magnetoresistance (CMR) manganite thin films, exhibit giant laser-induced thermoelectric voltage (LITV) effect due to anisotropic Seebeck effect and have a great potential for laser detector applications. In this work, we develop a novel time-integral type LaSrMnO thin-film laser energy meter based on anisotropic Seebeck effect. An epitaxial LaSrMnO thin film prepared by means of the pulsed laser deposition method onto a vicinal cut LaAlO3 substrate is irradiated by a 1064-nm Q-switched Nd:YAG laser and its 2nd (532 nm), 3rd (355 nm), and 4th (266 nm) harmonics at room temperature. The time integral of the LITV signal shows a good linear relationship with the laser energy per pulse in the measured wavelength range, which not only confirms the theoretical analysis, but also provides the basis for designing time-integral type laser energy meter. The advantages over other conventional laser detectors, such as fast (nanosecond order) response, spectrally broadband (from infrared to ultraviolet) and flat response, exceptional chemical and thermal stability, real-time measurement, and energy savings, make the device a promising candidate for next-generation laser detectors and laser energy/power meters.

Laser-Induced Thermoelectric Voltage in La<sub>0.5</sub>Pr<sub>0.5</sub>MnO<sub>3</sub> Thin Film

The laser-induced thermoelectric voltage was observed for the first time in praseodymium doped LaMnO3 thin film grown on LaAlO3 single crystal vicinal cut substrates by pulsed laser deposition. The experimental data for La0.5Pr0.5MnO3 showed a good liner relation between the voltage and the laser energy. The result suggested that the anisotropic Seebeck effect were responsible for the voltage signals in colossal magnetoresistance manganites thin film.

Influence of oxygen pressure on the lattice constants of Ba0.6Sr0.4TiO3 thin films and preparation of BaTiO3/Ba0.6Sr0.4TiO3 superlattices

Using pulsed laser deposition (PLD) technology, BaTiO3 (BT) and Ba0.6Sr0.4TiO3 (BST) single-layer films were successfully prepared through a series of optimization experiments. X-ray diffraction investigations indicated that BT and BST thin films were nearly (001)-epitaxially grown on LaAlO3 (001) substrates. And functional relation between the lattice constants of BST thin films and the oxygen pressure was close to Boltzmann function from 10-3 to 25 Pa. Then the high-quality BT/BST superlattices were also prepared under these optimal conditions. The surface topography measurement by atomic force microscopy (AFM) demonstrated that the root-mean-square (RMS) roughness of BT/BST superlattice was only 0.3048 nm. The surface smoothness has achieved the atomic scale. In addition, satellite peaks were clearly observed in the XRD spectrum. According to the position of satellite peaks that belong to (002) diffraction peak, the superperiod of superlattices was calculated and the deposition rates of BT and BST thin films were deduced. Finally, laser induced thermoelectric voltage (LITV) effect was measured for the first time in BT/BST superlattices grown on vicinal-cut single crystal substrates, which was not found in BT and BST single-layer films.

Effects of annealing atmosphere on thermoelectric signals from ZnO films

Zinc oxide epilayer films were grown on vicinal cut sapphire substrates by pulsed laser deposition with in situ annealing oxygen pressures varied from 0 to 10 × 10 3 Pa. The best crystalline quality was obtained for ZnO layer with annealing oxygen pressure of 6 × 10 3 Pa. Laser induced thermoelectric voltage (LITV) were observed along the tilting angle orientation of the substrate when the pulsed KrF excimer laser of 248 nm were irradiated on the films. The largest LITV signal was measured for the film grown at 6 × 10 3 Pa annealing oxygen pressure. According to the measured LITV signals, Seebeck anisotropy was evaluated and was found to range from 3 to 12 μV/K for ZnO films annealed at different oxygen pressures from 2 to 10 × 10 3 Pa. It is suggested that oxygen ambient plays an important role in the electronic properties of the ZnO films.

The transverse laser induced thermoelectric voltages in step flow growth (1 — x)Pb(Mg1/3Nb2/3)O3—xPbTiO3 thin films

This paper reports that the transverse laser induced thermoelectric voltages (LITV) are observed for the first time in the step flow growth (1 — x)Pb(Mg1/3Nb2/3)O3—xPbTiO3 (PMN-PT, x = 0.20, 0.33, 0.50) thin films deposited on vicinal-cut strontium titanate single crystal substrates. Because lead magnesium niobate-lead titanate is a solid solution of lead magnesium niobate (PMN) and lead titanate (PT), there are two types of signals. One is wide with a time response of a microsecond, and the other superimposed with the wide signal is narrow with a time response of a nanosecond. The transverse LITV signals depend on the ratio of PMN to PT drastically. Under the irradiation of 28-ns pulsed KrF excimer laser with the 248-nm wavelength, the largest induced voltage is observed in the 0.50Pb(Mg1/3Nb2/3)O3—0.50 PbTiO3 films. Moreover, the effects of film thickness, substrates, and tilt angles of substrates are also investigated.

PZT薄膜制备及激光感生热电电压研究

PZT薄膜制备及激光感生热电电压研究

Thermoelectric signals from Si/SiGe superlattices

p-Si/Si0.5Ge0.5 superlattices (SLs) grown on a vicinal-cut p-type silicon single crystalline substrate by molecular beam epitaxy (MBE) were irradiated by a KrF excimer laser. Two types of transient laser induced voltage (LIV) signals were observed, among which the signals of 0.3 V in amplitude with time response ∼40 ns showed up along the tilted directions, while voltage signals of ∼10 mV with a time response of tens of microseconds presented along the untilted directions which were perpendicular to the tilted direction. The results demonstrate that the observed photoelectric signals of 0.3V amplitude are laser induced thermoelectric voltages (LITV) due to the tilting angle relation. The observed LIV signals implied that these SLs exhibited anisotropic Seebeck components. It was also found that the LIV signals increased with the p-type doping level in the Si layer, which was coincident with the expectation of the laser induced thermoelectric effect. According to the measured signals and the theoretical formula, one can calculate the physical parameters of the SLs. The calculated effective Seebeck anisotropy coefficients (Sab − Sc) for samples with 1018 cm−3 and 1020 cm−3 are approximately 11.2 µV K−1 and 18.2 µV K−1, respectively.

Laser induced thermoelectric voltage effect in [formula omitted] ferroelectric thin film

Laser Induced Thermoelectric Voltage (LITV) effect was observed for the first time in Pb(Zr 0.3Ti 0.7)O 3(PZT) ferroelectric thin films grown on LaSrAlTaO 3(LSATO), LaAlO 3(LAO) and SrTiO 3(STO) single crystal vicinal cut substrates by pulsed laser deposition (PLD). LITV signals increase linearly with the single-pulse laser energy for c -axis orientated thin film. Such a linear relationship does not hold for a -axis orientated thin film. The result shows that the LITV effect in PZT thin film is originated from the atomic layer thermopile effect, in which anisotropy of Seebeck coefficient plays an important role.

Wide band-response laser-induced thermoelectric voltage in tilted orientation SrTiO 3 single-crystal coated by La 0.7Sr 0.3CoO 3 layer

With different wavelengths from the infrared (IR) to ultraviolet (UV) band, laser-induced thermoelectric voltage (LITV) has been observed in the vicinal cut SrTiO 3 (STO) single crystals, coated with La 0.7Sr 0.3CoO 3 (LSCO) layer. It is demonstrated that the polarity of voltage signal in the STO substrate is reversed when the STO substrate is illuminated by UV laser rather than by IR or visible laser. The polarity of voltage signal in LSCO film is always consistent with that from the STO substrate no matter 1064 or 355 nm laser irradiate the LSCO film or the STO substrate. A possible interpretation of the phenomenon is proposed.

Preparation and laser induced thermoelectric voltage effect of ［（SrTiO3）n/（SrTi0.8Nb0.2O3）m］20/LaAlO3 superlattices

The （SrTiO3）n/（SrTi0.8Nb0.2O3）m superlattices on vicinal-cut LaAlO3 （100） single crystal substrate with tilting angle 10° have been prepared using pulsed laser deposition. The superlattices were characterized by X-ray diffraction, in which regularly distributed satellite peak structure was observed. According to the position of satellite peaks, the superperiod of superlattices was calculated and the deposition rates of SrTiO3 and SrTi0.8Nb0．2Ｏ3 were deduced as 0.78 /pulse for SrTiO3 and 0.57 /pulse for SrTi0．8Nb0．2Ｏ3. In addition, laser induced thermoelectric voltage （LITV） effect was measured for the first time in these superlattice thin films. This phenomenon indieales that this kind of artificial atomic layer thermopile structure possesses Seebeck anisotropy. It was found that when the thickness of dielectric SrTiO3 layer n=46.8 nm, for conductive SrTi0．8Nb0．2Ｏ3 layer with m=19.0 nm and m=11.4 nm, the average peak voltage of LITV signals reaches the maximum U—P=0.7 V/mJ·mm, and the minimum average response time is τ—=124 ns, respectively.