Final Film Composition Research Articles

Thin-film CuIn1−xGaxSe2 photovoltaic cells from solution-based precursor layers

We have fabricated 15.4% and 12.4% efficient thin-film CuIn1−xGaxSe2 (CIGS)-based photovoltaic devices from solution-based electrodeposited (ED) and electroless-deposited (EL) precursors. As-deposited precursors are Cu-rich CIGS. Additional In, Ga, and Se are added to the ED and EL precursor films by physical vapor deposition (PVD) to adjust the final semiconductor film composition to CuIn1−xGaxSe2. The ED and EL device parameters are compared with those of a 17.7% PVD device. The tools used for comparison are current voltage, capacitance voltage, and spectral response characteristics.

Influence of processing parameters on dielectric properties of PZT thin films on steel substrates

PZT thin films with a stoichiometry close to the morphotropic phase boundary were prepared on metallic susbtrates by a modified sol get processing. Single layer film thicknesses of about 0.9 μm were obtained, by multiple coatings films up to 5 μm could be prepared. Hysteresis loops were obtained with a remanent polarization of about 35 μC/cm 2 and a coercivity of about 10 V/μm for an applied field strength of 50 V/μm. Dependent on the solvents used for the sol preparation the dielectric breakdown was about 50 V/μm for films with a high amount of triethanolamine (TEA) in the solution and more than 70 V/μm for films prepared with less TEA. By chemical analysis of the crystalline samples a significant lead loss was found compared to the lead content of the deposition solutions. By XRD measurements secondary phases were found for a molar lead excess of about 35 % in the deposition solutions. The influence of the lead content on the small and large signal dielectric properties was investigated. Best ferroelectric behavior was found for a molar lead excess of 30 % in the solutions, corresponding to a final film composition of Pb 1,10 Zr 0,53 Ti 0,47 O 3 .

Preparation of aluminum nitride films by low pressure organometallic chemical vapor deposition

The low pressure chemical vapor deposition of aluminum nitride films from hexakisdimethylamido-dialuminum (Al 2(N(CH 3) 2) 6) and ammonia has been studied. The deposition conditions were varied in order to establish the influence of deposition parameters on final film composition. The grown films were characterized by Fourier transform IR spectroscopy, showing an absorption peak at 680 cm −1. Only at low temperatures or for depositions without ammonia, are an absorption peak at 810 cm −1 and peaks at higher frequencies (3000–3500 cm −1) found. These contributions are due to a strong carbon incorporation as a result of precursor decomposition. The lowest temperature to obtain a film without ammonia was determined to be 473 K. Film compositions were found to be near stoichiometric for almost any deposition conditions, with N-to-Al ratios ranging between 0.9 and 1.

Preparation of aluminum nitride films by low pressure organometallic chemical vapor deposition

The low pressure chemical vapor deposition of aluminum nitride films from hexakisdimethylamido-dialuminum (Al2(N(CH3)2)6) and ammonia has been studied. The deposition conditions were varied in order to establish the influence of deposition parameters on final film composition. The grown films were characterized by Fourier transform IR spectroscopy, showing an absorption peak at 680 cm−1. Only at low temperatures or for depositions without ammonia, are an absorption peak at 810 cm−1 and peaks at higher frequencies (3000–3500 cm−1) found. These contributions are due to a strong carbon incorporation as a result of precursor decomposition. The lowest temperature to obtain a film without ammonia was determined to be 473 K. Film compositions were found to be near stoichiometric for almost any deposition conditions, with N-to-Al ratios ranging between 0.9 and 1.

Substrate bias effects on composition and coercivity of CoCrTa/Cr thin films on canasite and glass

CoCrTa/Cr thin films were prepared by rf diode sputtering onto canasite and glass substrates at various bias voltages from two targets of different compositions (Co82.8Cr14.6Ta2.6 and Co86Cr12Ta2). While Auger depth profile analysis indicates that there is some broadening at the CoCrTa-Cr interface, x-ray fluorescence spectroscopy reveals that changes in alloy composition due to the resputtering processes are even more prominent. For both targets, as the substrate bias increases the Co content in the films declines, and the magnetization decreases. The maximum film coercivity appears to correlate to the final film composition. By investigating the results from both targets, it is concluded that the coercivity reaches a maximum when the film composition is in the neighborhood of Co84Cr13Ta3. Thus, to optimize the coercivity different bias voltages are required for each target. Excessive substrate bias, however, leads to films with low magnetization and coercivity.