Structural and electrical properties of fluorine doped tin oxide films prepared by spray-pyrolysis technique

Fluorine doped SnO₂ films have been successfully prepared at optimized substrate temperature of 723 K by spray pyrolysis technique. The XRD analysis confirmed that films deposited with F/Sn ratio of 0.05 showed a partial amorphous nature whereas films deposited with F/Sn = 0.10 exhibited tetragonal structure (2 0 0) as the preferred orientation and polycrystalline structure. The lattice constants were found to be a = 0.4750 and c = 0.3197 nm. The theoretically constructed XRD pattern for SnO₂ was used to compare with experimental pattern, the difference between them is discussed. By using SEM analysis, the surface morphology of the films was observed as an effect of the variation of F/Sn ratio. At low temperature, the mobility due to lattice, polar, impurity, grain boundary and neutral scattering was estimated for SnO₂ and the possible scattering mechanisms were assigned to SnO₂:F films using experimentally obtained electrical data. The Mott parameters were determined by applying variable range hopping (VRH) conduction mechanism for SnO₂:F films (F/Sn = 0.05) where band conduction mechanism shifted to VRH conduction at below about 250 K.     

The enhanced conductivity and stability of AZO thin films with a TiO2 buffer layer

Aluminum doped zinc oxide (AZO) films were substitutes of the SnO₂:F films on soda lime glass substrate in the amorphous thin-film solar cells due to good properties and low cost. In order to improve properties of AZO films, the TiO₂ buffer layer had been introduced. AZO films with and without TiO₂ buffer layer were deposited on soda lime glass substrates by r.f. magnetron sputtering. Subsequently, one group samples were annealed in vacuum (0.1 Pa) at 500 °C for 120 s using the RTA system, and the influence of TiO₂ thickness on the properties of AZO films had been discussed. The XRD measurement results showed that all the films had a preferentially oriented (0 0 2) peak, and the intensity of (0 0 2) peak had been enhanced for the AZO films with TiO₂ buffer layer. The resistivity of TiO₂ (3.0 nm)/AZO double-layer film is 4.76×10⁻⁴ Ω cm with the maximum figure merit of 1.92×10⁻² Ω⁻¹, and the resistivity has a remarkable 28.7% decrease comparing with that of the single AZO film. The carrier scattering mechanism of TiO₂ (3.0 nm)/AZO double-layer film had been described by Hall measurement in different temperatures. The average transmittance of all the films exceeded 92% in the visible spectrum. Another group samples were heat treated in the quartz tube in air atmosphere, and the effect of TiO₂ thickness on thermal stability of AZO films had been discussed.     

Annealing temperature influence on electrical properties of ion beam sputtered Bi2Te3 thin films

Ion beam sputtering process was used to deposit n-type fine-grained Bi₂Te₃ thin films on BK7 glass substrates at room temperature. In order to enhance the thermoelectric properties, thin films are annealed at the temperatures ranging from 100 to 400 °C. X-ray diffraction (XRD) shows that the films have preferred orientations in the c-axis direction. It is confirmed that grain growth and crystallization along the c-axis are enhanced as the annealing temperature increased. However, broad impurity peaks related to some oxygen traces increase when the annealing temperature reached 400 °C. Thermoelectric properties of Bi₂Te₃ thin films were investigated at room temperature. The Bi₂Te₃ thin films, including as-deposited, exhibit the Seebeck coefficients of −90 to −168 μV K⁻¹ and the electrical conductivities of 3.92×10²-7.20×10² S cm⁻¹ after annealing. The Bi₂Te₃ film with a maximum power factor of 1.10×10⁻³ Wm⁻¹ K⁻² is achieved when annealed at 300 °C. As a result, both structural and transport properties have been found to be strongly affected by annealing treatment. It was considered that the annealing conditions reduce the number of potential scattering sites at grain boundaries and defects, thus improving the thermoelectric properties.     

Properties of highly oriented spray-deposited fluorine-doped tin oxide thin films on glass substrates of different thickness

Transparent conducting thin films of fluorine-doped tin oxide (FTO) have been deposited onto the preheated glass substrates of different thickness by spray pyrolysis process using SnCl₄·5H₂O and NH₄F precursors. Substrate thickness is varied from 1 to 6 mm. The films are grown using mixed solvent with propane-2-ol as organic solvent and distilled water at optimized substrate temperature of 475 °C. Films of thickness up to 1525 nm are grown by a fine spray of the source solution using compressed air as a carrier gas. The films have been characterized by the techniques such as X-ray diffraction, optical absorption, van der Pauw technique, and Hall effect. The as-deposited films are preferentially oriented along the (2 0 0) plane and are of polycrystalline SnO₂ with a tetragonal crystal structure having the texture coefficient of 6.19 for the films deposited on 4 mm thick substrate. The lattice parameter values remain unchanged with the substrate thickness. The grain size varies between 38 and 48 nm. The films exhibit moderate optical transmission up to 70% at 550 nm. The figure of merit (φ) varies from 1.36×10⁻⁴ to 1.93×10⁻³ Ω⁻¹. The films are heavily doped, therefore degenerate and exhibit n-type electrical conductivity. The lowest sheet resistance (R_s) of 7.5 Ω is obtained for a typical sample deposited on 4 mm thick substrate. The resistivity (ρ) and carrier concentration (n_D) vary over 8.38×10⁻⁴ to 2.95×10⁻³ Ω cm and 4.03×10²⁰ to 2.69×10²¹ cm⁻³, respectively.     

Effect of process parameters on surface morphology and characterization of PE-ALD SnO2 thin films for gas sensing

Tin dioxide (SnO₂) thin films were deposited by plasma enhanced-atomic layer deposition (PE-ALD) on Si(1 0 0) substrate using dibutyl tin diacetate (DBTA) ((CH₃CO₂)₂Sn[(CH₂)₃-CH₃]₂) as precursor. The process parameters were optimized as a function of substrate temperature, source temperature and purging time. It is observed that the surface phenomenon of the thin films was changed with film thickness. Atomic force microscopy (AFM) images and X-ray diffraction (XRD) pattern were used to observe the texture and crystallanity of the films. The films deposited for 100, 200 and 400 cycles were characterized by XPS to determine the chemical bonding properties. XPS results reveal that the surface dominant oxygen species for 100, 200 and 400 cycles deposited films are O₂⁻, O⁻ and O²⁻, respectively. The 200 cycles film has exhibited highest concentration of oxygen (O⁻) species before and after annealing. Conductivity studies revel that this film has best adsorption strength to the oxygen ions forming on the surface. The sensor with 200 cycles SnO₂ thin film has shown highest sensitivity to CO gas than other films. A correlation between the characteristics of Sn3d_5/2 and O1s XPS spectra before and after annealing and the electrical behavior of the SnO₂ thin films is established.     

An atomic force microscopy study of DNA hairpin probes monolabelled with gold nanoparticle: Grafting and hybridization on oxide thin films

First and original results are reported regarding the surface evolution of two kinds of oxide film after covalent grafting and hybridization of hairpin oligonucleotide probes. These hairpin probes were monolabelled with a 1.4 nm gold nanoparticle. One kind of oxide film was rough Sb doped SnO₂ oxide film and the other kind was smooth SiO₂ film. Same process of covalent grafting, involving a silanization step, was performed on both oxide surfaces. Atomic force microscopy (AFM) was used to study the evolution of each oxide surface after different steps of the process: functionalization, probe grafting and hybridization. In the case of rough SnO₂ films, a slight decrease of the roughness was observed after each step whereas in the case of smooth SiO₂ films, a maximum of roughness was obtained after probe grafting. Step height measurements of grafted probes could be performed on SiO₂ leading to an apparent thickness of around 3.7 ± 1.0 nm. After hybridization, on the granular surface of SnO₂, by coupling AFM with SEM FEG analyses, dispersed and well-resolved groups of gold nanoparticles linked to DNA duplexes could be observed. Their density varied from 6.6 ± 0.3 × 10¹⁰ to 2.3 ± 0.3 × 10¹¹ dots cm⁻². On the contrary, on smooth SiO₂ surface, the DNA duplexes behave like a dense carpet of globular structures with a density of 2.9 ± 0.5 × 10¹¹ globular structures cm⁻².     

Annealing induced microstructural evolution of electrodeposited electrochromic tungsten oxide films

A significant influence of microstructure on the electrochromic and electrochemical performance characteristics of tungsten oxide (WO₃) films potentiostatically electrodeposited from a peroxopolytungstic acid (PPTA) sol has been evaluated as a function of annealing temperature. Powerful probes like X-ray diffractometry (XRD), transmission electron microscopy (TEM), UV-vis spectrophotometry, multiple step chronoamperometry and cyclic voltammetry have been employed for the thin film characterization. The as-deposited and the film annealed at 60 °C are composed of nanosized grains with a dominant amorphous phase, as well as open structure which ensues from a nanoporous matrix. This ensures a greater number of electroactive sites and a higher reaction area thereby manifesting in electrochromic responses superior to that of the films annealed at higher temperatures. The films annealed at temperatures ≥250 °C are characterized by a prominent triclinic crystalline structure and a hexagonal phase co-exists at temperatures ≥400 °C. The deleterious effect on the electrochromic properties of the film with annealing is ascribed to the loss of porosity, densification and the increasing crystallinity and grain size. Amongst all films under investigation, the film annealed at 60 °C exhibits a high transmission modulation (ΔT ∼ 68%) and coloration efficiency (η ∼ 77.6 cm² C⁻¹) at λ = 632.8 nm, charge storage capacity (Q_ins ∼ 21 mC cm⁻²), diffusion coefficient (6.08 × 10⁻¹⁰ cm² s⁻¹), fast color-bleach kinetics (t_c ∼ 275 s and t_b ∼ 12.5 s) and good electrochemical activity, as well as reversibility for the lithium insertion-extraction process upon cycling. The remarkable potential, which the film annealed at 60 °C has, for practical “smart window” applications has been demonstrated.     

Effects of SnO2 surface coating on the degradation of ZnS thin film phosphor

Pulsed laser deposited ZnS bare and SnO₂ coated ultra thin films were subjected to prolonged electron beam bombardment with 2 keV energy and a steady 44 mA/cm² current density, in 1 × 10⁻⁶ Torr O₂ pressure backfilled from a base pressure of 3 × 10⁻⁹ Torr at room temperature. Auger electron spectroscopy (AES) was used to monitor changes of the surface chemical composition of both the bare and coated phosphor films during electron bombardment. Degradation was manifested by the decrease of sulphur and accumulation of oxygen on the surface of the bare phosphor. However, with the SnO₂ coating this phenomenon was delayed until the protective SnO₂ was depleted on the surface through dissociation and reduction.     

Microstructural and electrochromic properties of tungsten oxide thin films produced by surfactant mediated electrodeposition

By electrochemically controlling the structure of the surface aggregates, the grain microstructure has been optimized to yield mesoporous thin films of tungsten oxide (WO₃) at the electrode-electrolyte interface in a peroxotungstate sol in the presence of a structure-directing agent (Triton) at room temperature. Apart from the dominant ultrafine nanocrystallites and pores (5-10 nm), well-developed abutting grains (25-100 nm) and nanofibrils also constitute an integral part of the film matrix. X-ray photoemission spectra reveal the as-deposited film (WO_3−x) to be constituted by a high proportion of W⁶⁺ states with a low oxygen deficiency (x = 0.02). A relatively high W⁵⁺ content in the film, upon intercalation of 18 mC cm⁻² charge translates into a large coloring efficiency (η_VIS ∼ 70 cm² C⁻¹) and transmission modulation. At a lithium intercalation level of 22 mC cm⁻², in addition to W⁵⁺ and W⁶⁺ states, the film also comprises of W⁴⁺ states. The extremely fast color-bleach kinetics (3 and 2 s, respectively, for a 50% change in transmittance) shown by the as-deposited WO₃ film are repercussions of the mesopore morphology, the multiple nanostructures and the sixfold channels of its hexagonal modification. The film shows a high cycling stability as the switching times do not show any significant decline even after 3500 repetitive cycles. Coloration efficiency over the solar and photopic regions and current density for lithium intercalation for the as-deposited film are superior to that observed for the films annealed at 100, 250 and 500 °C. The abysmal electrochromic response of the annealed films is a consequence of surface defects like cracks and uncontrolled densification and pore shrinkage.     

Chemical synthesis of nanocrystalline SnO2 thin films for supercapacitor application

Nanocrystalline SnO₂ thin films were deposited by simple and inexpensive chemical route. The films were characterized for their structural, morphological, wettability and electrochemical properties using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy techniques (SEM), transmission electron microscopy (TEM), contact angle measurement, and cyclic voltammetry techniques. The XRD study revealed the deposited films were nanocrystalline with tetragonal rutile structure of SnO₂. The FT-IR studies confirmed the formation of SnO₂ with the characteristic vibrational mode of Sn-O. The SEM studies showed formation of loosely connected agglomerates with average size of 5-10 nm as observed from TEM studies. The surface wettability showed the hydrophilic nature of SnO₂ thin film (water contact angle 9°). The SnO₂ showed a maximum specific capacitance of 66 F g⁻¹ in 0.5 Na₂SO₄ electrolyte at 10 mV s⁻¹ scan rate.     

Surface textured ZnO:Al thin films by pulsed DC magnetron sputtering for thin film solar cells applications

Transparent conducting thin films of ZnO:Al (Al-doped ZnO, AZO) were prepared via pulsed DC magnetron sputtering with good transparency and relatively lower resistivity. The AZO films with 800 nm in thickness were deposited on soda-lime glass substrates keeping at 473 K under 0.4 Pa working pressure, 150 W power, 100 μs duty time, 5 μs pulse reverse time, 10 kHz pulse frequency and 95% duty cycle. The as-deposited AZO thin films has resistivity of 6.39 × 10⁻⁴ Ω cm measured at room temperature with average visible optical transmittance, T_total of 81.9% under which the carrier concentration and mobility were 1.95 × 10²¹ cm⁻³ and 5.02 cm² V⁻¹ s⁻¹, respectively. The films were further etched in different aqueous solutions, 0.5% HCl, 5% oxalic acid, 33% KOH, to conform light scattering properties. The resultant films etched in 0.5% HCl solution for 30 s exhibited high T_total = 78.4% with haze value, H_T = 0.1 and good electrical properties, ρ = 8.5 × 10⁻⁴ Ω cm while those etched in 5% oxalic acid for 150 s had desirable H_T = 0.2 and relatively low electrical resistivity, ρ = 7.9 × 10⁻⁴ Ω cm. However, the visible transmittance, T_total was declined to 72.1%.     

Effects of vanadium doping on structure and electrical properties of SrBi4Ti4O15 thin films

The effects of vanadium(V) doping into SrBi₄Ti₄O₁₅ (SBTi) thin films on the structure, ferroelectric, leakage current, dielectric, and fatigue properties have been studied. X-ray diffraction result showed that the crystal structure of the SBTi thin films with and without vanadium is the same. Enhanced ferroelectricity was observed in the V-doped SrBi₄Ti₄O₁₅ (SrBi_4−x/3Ti_4−xV_xO₁₅, SBTiV-x (x = 0.03, 0.06, and 0.09)) thin films compared to the pure SrBi₄Ti₄O₁₅ thin film. The values of remnant polarization (2P_r) and coercive field (2E_c) of the SBTiV-0.09 thin film capacitor were 40.9 μC/cm² and 105.6 kV/cm at an applied electric field of 187.5 kV/cm, respectively. The 2P_r value is over five times larger than that of the pure SBTi thin film capacitor. At 100 kHz, the values of dielectric constant and dielectric loss were 449 and 0.04, and 214 and 0.06 for the SBTiV-0.09 and the pure SBTi thin film capacitors, respectively. The leakage current density of the SBTiV-0.09 thin film capacitor measured at 100 kV/cm was 6.8 × 10⁻⁹ A/cm², which is more than two and a half orders of magnitude lower than that of the pure SBTi thin film capacitor. Furthermore, the SBTiV-0.09 thin film exhibited good fatigue endurance up to 10¹⁰ switching cycles. The improved electrical properties may be related to the reduction of internal defects such as bismuth and oxygen vacancies with changes in the grain size by doping of vanadium into SBTi.     

A study of the optical properties of titanium oxide films prepared by dc reactive magnetron sputtering

TiO₂ thin films were deposited on the glass substrates by dc reactive magnetron sputtering technique at different sputtering pressures (2 × 10⁻³ to 2 × 10⁻² mbar). The films prepared at low pressures have an anatase phase, and the films prepared at high pressures have an amorphous phase. The optical properties were studied by measuring the transmittance and the ellipsometric spectra. The optical constants of the films in the visible range were obtained by fitting the transmittance combined with the ellipsometry measurements using the classical model with one oscillator. The refractive index of the films decreases from 2.5 until 2.1 as the sputtering pressure increases from 2 × 10⁻³ to 2 × 10⁻² mbar. The films prepared at the pressure higher than 6 × 10⁻³ mbar show a volume inhomogeneity. This volume inhomogeneity has been calculated by fitting the transmittance and the ellipsometric spectra. The volume inhomogeneity of the film prepared at the highest sputtering pressure is about 10%. Although the films prepared at high pressures show a large volume inhomogeneity, they have low extinction coefficients. It is suggested that the anatase phase results in more light scattering than amorphous phase does, and then a high extinction coefficient.     

Characterization of nanocrystalline SnO2 thin film fabricated by electrodeposition method for dye-sensitized solar cell application

Nanocrystalline SnO₂ thin film was prepared by cathodic electrodeposition-anodic oxidation and its structure was characterized by X-ray diffraction, SEM, UV-visible absorption and nitrogen adsorption-desorption by BET method. The obtained film has a surface area of 137.9 m²/g with grain sized of 24 nm. Thus the prepared SnO₂ thin film can be applied as an electrode in dye-sensitized solar cell. The SnO₂ electrode was successfully sensitized by Erythrosin dye and photoelectrochemical measurements indicate that the cell present short-circuit photocurrent (J_sc) of 760 μA/cm², fill factor (FF = 0.4), photovoltage (V_oc = 0.21 V) and overall conversion efficiency (η) of 0.06% under direct sun light illumination. The relatively low fill factor and photovoltage are attributed to the reduction of triodiode by conduction band electrons and intrinsic properties of SnO₂.     

Nonlinear optical properties in SrTiO3 thin films by pulsed laser deposition

Well-crystallized 250 nm-thick SrTiO₃ thin films on fused-quartz substrate were prepared by pulsed laser deposition. The band-gap of SrTiO₃ thin film by transmittance spectra is equal to 3.50 eV, larger than 3.22 eV for the bulk crystal. The nonlinear optical properties of the films were examined with picosecond pulses at 1.064 μm excitation. A large two-photon absorption (TPA) with absorption coefficient of 87.7 cm/GW was obtained, larger than 51.7 cm/GW for BaTiO₃ thin films. The nonlinear refractive index n₂ is equal to 5.7×10⁻¹⁰ esu with a negative sign, larger than 0.267×10⁻¹¹ esu for bulk SrTiO₃. The large TPA is attributed to intermediate energy levels introduced by the grain boundaries, and the optical limiting behaviors stemming from both TPA and negative nonlinear refraction were also discussed.     

Structural, optical properties and VCNR mechanisms in vacuum evaporated iodine doped ZnSe thin films

Iodine doped ZnSe thin films were prepared onto uncoated and aluminium (Al) coated glass substrates using vacuum evaporation technique under a vacuum of 3 × 10⁻⁵ Torr. The composition, structural, optical and electrical properties of the deposited films were analyzed using Rutherford backscattering spectrometry (RBS), X-ray diffraction (XRD), spectroscopic ellipsometry (SE) and study of I-V characteristics, respectively. In the RBS analysis, the composition of the deposited film is calculated as ZnSeI_0.003. The X-ray diffractograms reveals the cubic structure of the film oriented along (1 1 1) direction. The structural parameters such as crystallite size, strain and dislocation density values are calculated as 32.98 nm, 1.193 × 10⁻³ lin⁻² m⁻⁴ and 9.55 × 10¹⁴ lin/m², respectively. Spectroscopic ellipsometric (SE) measurements were also presented for the prepared iodine doped ZnSe thin films. The optical band gap value of the deposited films was calculated as 2.681 eV by using the optical transmittance measurements and the results are discussed. In the electrical studies, the deposited films exhibit the VCNR conduction mechanism. The iodine doped ZnSe films show the non-linear I-V characteristics and switching phenomena.     

Identification of optical nonlinearities of dye-doped nematic and polymer-dispersed liquid crystals using Z-scan technique

This study investigates the nonlinear optical properties of azo-dye-doped nematic and polymer-dispersed liquid crystal (ADDPDLC) films with nano-sized LC droplets using the Z-scan technique, which is a simple but powerful technique for measuring the optical Kerr constants of materials. The results indicate that the optical Kerr constant (n₂) of the azo-dye-doped nematic LC (ADDLC) film is large because of the photoisomerization effect and the thermal effect. Therefore, the optical Kerr constant of this material can be modulated by varying the temperature of the sample and the direction of polarization of incident laser. The range of n₂ modulated is from −5.26 × 10⁻³ to 1.62 × 10⁻³ cm²/W. The optical Kerr constants of ADDPDLC films at various temperatures are also measured. The experimental results reveal that liquid crystals in the ADDPDLC film strengthen the nonlinearity. The n₂ of the ADDPDLC film is maximal at ∼35 °C, because of the decrease in the clearing temperature of the ADDPDLC films. The clearing temperatures of the liquid crystals (E7), and the ADDPDLC film used in this work were found to be 61 °C and 43 °C, respectively.     

Transparent and conducting Zn-Sn-O thin films prepared by combinatorial approach

Zn-Sn-O (ZTO) films with continuous compositional gradient of Sn 16-89 at.% were prepared by co-sputtering of two targets of ZnO and SnO₂ in a combinatorial method. The resistivities of the ZTO films were severely dependent on oxygen content in sputtering gas and Zn/Sn ratio. Except for the films with Sn 16 at.%, all the as-prepared films were amorphous and maintaining the stable amorphous states up to the annealing temperature of 450 °C. Annealing at 650 °C resulted in crystallization for all the composition, in which ZnO, Zn₂SnO₄, ZnSnO₃, and SnO₂ peaks were appeared successively with increasing Sn content. Above Sn 54 at.%, the ZTO films were deduced to have a local structure mixed with ZnSnO₃ and SnO₂ phases which were more conductive and stable in thermal oxidation than ZnO and Zn₂SnO₄ phases. The lowest resistivity of 1.9 × 10⁻³ Ω cm was obtained for the films with Sn 89 at.% when annealed at 450 °C in a vacuum. The carrier concentrations of the amorphous ZTO films that contained Sn contents higher than 36 at.% and annealed at 450 °C in a vacuum were proportional to the Sn contents, while the Hall mobilities were insensitive to Sn contents and leveling in the range of 23-26 cm²/V s.     

Drude's model calculation rule on electrical transport in Sb-doped SnO2 thin films, deposited via sol-gel

The evaluation of free carrier concentration based on Drude's theory can be performed by the use of optical transmittance in the range 800-2000 nm (near infrared) for Sb-doped SnO₂ thin films. In this article, we estimate the free carrier concentration for these films, which are deposited via sol-gel dip-coating. At approximately 900 nm, there is a separation among transmittance curves of doped and undoped samples. The plasma resonance phenomena approach leads to free carrier concentration of about 5×10²⁰ cm⁻³. The increase in the Sb concentration increases the film conductivity; however, the magnitude of measured resistivity is still very high. The only way to combine such a high free carrier concentration with a rather low conductivity is to have a very low mobility. It becomes possible when the crystallite dimensions are taken into account. We obtain grains with 5 nm of average size by estimating the grain size from X-ray diffraction data, and by using line broadening in the diffraction pattern. The low conductivity is due to very intense scattering at the grain boundary, which is created by the presence of a large amount of nanoscopic crystallites. Such a result is in accordance with X-ray photoemission spectroscopy data that pointed to Sb incorporation proportional to the free electron concentration, evaluated according to Drude's model.     

Ferromagnetism in amorphous Ge1−xMnx grown by low temperature vapor deposition

Magnetic properties of amorphous Ge_1−xMn_x thin films were investigated. The thin films were grown at 373 K on (100) Si wafers by using a thermal evaporator. Growth rate was ∼35 nm/min and average film thickness was around 500 nm. The electrical resistivities of Ge_1−xMn_x thin films are 5.0×10⁻⁴∼100 Ω cm at room temperature and decrease with increasing Mn concentration. Low temperature magnetization characteristics and magnetic hysteresis loops measured at various temperatures show that the amorphous Ge_1−xMn_x thin films are ferromagnetic but the ferromagnetic magnetizations are changing gradually into paramagnetic as increasing temperature. Curie temperature and saturation magnetization vary with Mn concentration. Curie temperature of the deposited films is 80-160 K, and saturation magnetization is 35-100 emu/cc at 5 K. Hall effect measurement at room temperature shows the amorphous Ge_1−xMn_x thin films have p-type carrier and hole densities are in the range from 7×10¹⁷ to 2×10²² cm⁻³.