Effect Of Laser Annealing Research Articles

Effects of thermal and laser annealing on the structure of Ge2Sb2Te5 thin films

In this study, we used Raman spectroscopy to compare the local structure of Ge2Sb2Te5 (GST) thin films with thicknesses of 90 nm and 271 nm that were crystallized through thermal annealing and laser radiation (laser annealing) during the recording of Raman spectra in situ. We found that for all crystallized films, the position of the main peaks in the Raman spectra was almost the same, and their structure corresponded to a hexagonal close packed state. It is noteworthy that the full width at half maximum (FWHM) of the main peaks varies considerably depending on the crystallization method used.

Fabrication of nitrogen-hyperdoped silicon by high-pressure gas immersion excimer laser doping

In recent years, research on hyperdoped semiconductors has accelerated, displaying dopant concentrations far exceeding solubility limits to surpass the limitations of conventionally doped materials. Nitrogen defects in silicon have been extensively investigated for their unique characteristics compared to other pnictogen dopants. However, previous practical investigations have encountered challenges in achieving high nitrogen defect concentrations due to the low solubility and diffusivity of nitrogen in silicon, and the necessary non-equilibrium techniques, such as ion implantation, resulting in crystal damage and amorphisation. In this study, we present a single-step technique called high-pressure gas immersion excimer laser doping (HP-GIELD) to manufacture nitrogen-hyperdoped silicon. Our approach offers ultrafast processing, scalability, high control, and reproducibility. Employing HP-GIELD, we achieved nitrogen concentrations exceeding 6 at% (3.01 × 1021 at/cm3) in intrinsic silicon. Notably, nitrogen concentration remained above the liquid solubility limit to ~1 µm in depth. HP-GIELD’s high-pressure environment effectively suppressed physical surface damage and the generation of silicon dangling bonds, while the well-known effects of pulsed laser annealing (PLA) preserved crystallinity. Additionally, we conducted a theoretical analysis of light-matter interactions and thermal effects governing nitrogen diffusion during HP-GIELD, which provided insights into the doping mechanism. Leveraging excimer lasers, our method is well-suited for integration into high-volume semiconductor manufacturing, particularly front-end-of-line processes.

Influence of XeCl excimer laser annealing on the ferroelectric nondoped HfO2 formation deposited on a Si(100) substrate

In this research, we have investigated the effect of excimer laser annealing (ELA) on the ferroelectric nondoped HfO2 (FeND-HfO2) formation deposited on a Si(100) substrate. The XeCl (λ: 308 nm) ELA was irradiated as post-deposition annealing (PDA) in the N2 ambient to the 10 nm thick HfO2 deposited by RF-magnetron sputtering without substrate heating. The C–V characteristics of Al/HfO2/p-Si(100) metal/ferroelectrics/Si (MFS) diodes were gradually improved with the energy density of ELS from 170 mJ cm−2 to 270 mJ cm−2 irradiated at 200 Hz for 200 shots although the charge-injection type hysteresis of 0.2–0.3 V remained. The post-metallization annealing (PMA) at 400 °C/5 min in N2/4.9%H2 ambient for Al/HfO2/p-Si(100) MFS diodes markedly improved the C–V characteristics, and negligible hysteresis with ideal flat-band voltage (V FB) was realized. The memory window (MW) of 0.42 V was achieved by the program/erase (P/E) operation with the input pulses of +3 V/100 ms and −8 V/100 ms for the MFS diode with an ELA energy density of 270 mJ cm−2 at 200 Hz for 200 shots followed by the PMA.

Nanosecond pulsed laser etching anti-reflective gratings and synchronous laser annealing for performance optimization of Ag/AZO thin films

Nanosecond pulsed laser etching for fabricating anti-reflective gratings and inducing synchronous laser annealing was performed on Ag/AZO films. The optimum grating pitch was determined by performance analyses of laser-etched unidirectional gratings, based on which laser-etched bidirectional gratings were fabricated to further determine the optimum grating tilt angle. The results revealed that with the increase of grating pitch, the grating ridge total-side-area was gradually decreased to cause a gradually weakened anti-reflective effect, but the superimposed heat-affected zones between adjacent grooves became smaller or even disappeared, which brought about different synchronous laser annealing effects. The unidirectional grating-textured film with a medium grating pitch of 200 μm showed the best overall performance under the combined influence from anti-reflective gratings and synchronous laser annealing. For the bidirectional gratings, although increasing the grating tilt angle did not change the grating ridge total-side-area, it would enable the laser energy to be more uniformly distributed on the whole film surface, producing a better synchronous laser annealing effect. The bidirectional grating-textured film with a grating tilt angle of 90° had the best overall performance with the highest FOM value of 2.18 × 10−2 Ω−1 that was ∼3.2 times that of the as-prepared film. The results are instructive for preparing high-performance TCO-based films.

The influence of laser-annealing pulse width on optical transparency and carrier dynamics of ITO thin films

Indium tin oxide (ITO) has important application in photoelectronic and photonic devices, demanding effective approach and appropriate parameters to modulate the ITO properties. The effects of laser annealing at 1064 nm with different pulse width (875 ps, 10 ns, and 300 ns) on optical and nonlinear optical properties of ITO films were investigated. Compared with 875 ps and 10 ns, laser annealing at 300 ns significantly improved the near-infrared transmittance of ITO films. The change arises from the elimination of oxygen vacancies and reduction of tin oxides, resulting in the decrease of carrier concentration. Finite element simulations indicate that laser annealing with pulse width of 875 ps and 10 ns have high instantaneous peak temperatures of 1128.5 K and 783 K, respectively, while the temperature accumulation between pulses is negligible. On the contrary, the laser annealing with a pulse width of 300 nshas lower peak transient temperature of 343 K but high static residence temperature of 973 K. The results reveal that the modification of ITO films depends more on the static average temperature rather than the instantaneous peak temperature. The modulation of carrier dynamics in both amplitude and temporal domain was demonstrated after 300 ns laser annealing, achieving ultrafast transient response approximately 150 fs. This work provides theoretical and experimental basis for us to select suitable laser conditions for directional annealing of ITO film to make it suitable for the applications of broad optical spectrum photovoltaic devices or ultrafast optical exchange for high-speed data processing.

Pulsed laser annealed rare earth doped TiO2 thin films for luminescence and sensing applications

Many research activities target functional luminescent materials based on metal oxides activated with trivalent rare earth ions. Specific applications necessitate optimization of material preparation, annealing and excitation-detection techniques. Hereby we utilized pulsed laser deposition to obtain thin (150 nm) TiO2 films containing 1at% of samarium (Sm) or neodymium (Nd) impurity ions. The effect of pulsed laser annealing (ArF excimer laser, wavelength 193 nm, pulse duration 20 ns) on their structural and luminescent properties was investigated. It was found that, compared to conventional thermal annealing at 700 °C, proper laser annealing (fluence 50 mJ/cm2, 5–15 shots) induced much better crystallization (nearly phase-pure anatase) along with respective improvement of host-sensitized trivalent rare earth fluorescence. The outcome significantly depends on the applied fluence and number of laser shots. Effects of under- and overannealing were witnessed (poor or mixed phase crystallization, weak luminescence and melting/dewetting of the film). A strong luminescence from optimally annealed samples was detected under excitation of 365 nm light emitting diode, which is favorable for potential applications of such thin films. As an example, trace oxygen sensing is demonstrated with the laser annealed TiO2:Sm film.

Effect of Laser annealing on structural and thermoelectric properties of SnSe thin films

This study adopted the flash evaporation technique to prepare SnSe thin films onto glass substrates kept at room temperature. The effect of CO2 laser annealing on the structural properties and thermoelectric characterizations of SnSe films was investigated in power annealing (10 W) at (10,15,20 Min). Morphologies and structures of the crystalline were determined using an atomic force microscope and X-ray diffraction. Power factor, electrical conductivity, and the Seebeck coefficients were determined. The results demonstrated that the power factor and the Seebeck coefficient were enhanced as the annealing time increased. When the annealing time reaches twenty minutes at 500K, the power factor and Seebeck coefficient of SnSe thin films were found to be about 6.33 μW/cm.K2 and 650 μV/K., respectively.

Effect of laser annealing on the properties of Ag/ZnO nanostructures

Ag/ZnO nanostructures were synthesized using pulsed laser deposition (PLD) in open air (at atmospheric pressure). The deposition was carried out by a Nd:YAG laser, with the Ag layer composed of nanoparticles grown on SiO2 (001) substrates by the laser wavelength of 355 nm; this layer was covered by ZnO deposited by using the laser wavelength of 1064 nm. The samples were laser annealed, which led to a modification of the nanoparticles. The nanocomposites produced were characterized by TEM, UV-Vis and PL spectroscopy. The annealing procedures influence the optical properties of the Ag/ZnO nanocomposites. The laser annealing under certain parameters changes the emission behavior of the Ag/ZnO nanocomposite heterostructures. By employing localized surface plasmon resonance (LSPR), the near band edge (NBE) emission intensity of the ZnO films composed of nanoparticles was varied. An enhancement of the UV emission located at about 383 nm, commonly attributed to an excitonic transition, was registered after laser annealing with one pulse at the wavelength of 355 nm. The results obtained demonstrate that the annealing of Ag/ZnO composite nanostructures plays a key role in tuning the PL performance of a semiconductor material where an LSPR occurs.

Investigation of minority carrier traps in p-type mc-Si: Effect of firing and laser annealing

Recently, it has been shown that the investigation of minority carrier traps (traps) is a useful method to study defects in silicon wafers. In this paper, we report the presence of traps in p-type multicrystalline silicon with a photoconductance decay time constant of 1.9 ± 0.4 s (at 30 °C). It is shown that the density of traps is significantly reduced after firing. However, this reduction in trap density is metastable, and it recovers by short dark annealing at 100 °C or after several days of storage at room temperature. In contrast, laser annealing is shown to eliminate the traps in fired wafers, while no change in the trap density is observed for wafers that have not been fired. Further dark annealing of those wafers does not recover the traps, suggesting that this trap annihilation is not reversible.

Effects of laser annealing on polymer sheets using a laser-diode with a wavelength of 408 nm

Transparent polymer sheets (PET, PEN, PI) were treated in a vacuum condition by a laser-diode (wavelength: 408 nm). The polymers were decomposed thermally with an endothermic reaction by the laser heating, and carbonization, due to the evolution of gaseous products including CO and CO2, occurred on the surface. The heating mechanism of the polymers was summarized as the formation of carbonized layer on polymer sheets and the thermal conduction due to the heating of carbonized layer by the laser-diode. Thus, it is concluded that the choice of an appropriate wavelength for the laser-diode can facilitate modification processes for various transparent polymers.

Pulsed laser modification of layered B-C and mixed BCx films on sapphire substrate

The effect of pulsed laser annealing (PLA, i.e., action of nanosecond laser pulses in air atmosphere) on surface morphology, structure, chemical state, and electrical properties of thin films consisting of boron and carbon atoms was studied. The nanolayered В/С and mixed ВСx~3 thin film precursors (with a thickness ~110–140 nm) were created on sapphire substrates by using the pulsed laser deposition. Scanning electron microscopy and Raman scattering measurements indicate that the process of stratification of the multilayer B/C films dominated during PLA of the films. The outer layers were removed, and closer to the substrate, the B and C layers were preserved, and they were not mixed. For the mixed ВСх films deposited at elevated temperatures, the PLA treatment enhances ordering of initially amorphous film structure. At the stage of melting of these films, oxygen (from surrounded air) penetrated inside the top layer of the film leading to the formation of a multiphase structure from g-BCx and B-doped GO/rGO after solidification. Studies of the chemical state of elements in the irradiated film have shown that О atoms, which penetrated the under-surface layers of the film, facilitated the formation of new chemical bonds in the B–C–O system. The concentration of O atoms in the depth of the film could reach 8%. The preferential oxidation of boron in a homogeneous mixture of B–C–O atoms indicated that intercalation of carbon matrix could be due to the incorporation of not only O atoms, but also B–O molecules. The laser irradiated ВСх films have a relatively low resistivity (~1.6 mΩ·cm) and semi-metallic dependence on temperature in the range 4.2–300 К. The spatial distribution of conductivity zones after PLA has an irregular structure, and its pattern looks like sand dunes, indicating that the PLA treatment leads to mixing zones of high with those of lower conductivity. The contact-tip resistivity inside the areas of high conductivity of the ВСx/Al2O3 samples may be significantly lower than that of pure graphite.

Laser annealing towards high-performance monolayer MoS2 and WSe2 field effect transistors

The transition metal dichalcogenides (TMDCs) have been intensively investigated as promising nanoelectronic and optoelectronic materials. However, the pervasive adsorbates on the surfaces of monolayer TMDCs, including oxygen and water molecules from the ambient environment, tend to degrade the device performance, thus hindering specific applications. In this work, we report the effect of laser irradiation on the transport and photoresponse of monolayer MoS2 and WSe2 devices, and this laser annealing process is demonstrated as a straightforward approach to remove physically adsorbed contaminants. Compared to vacuum pumping and in situ thermal annealing treatments, the field-effect transistors after laser annealing show a more than one order of magnitude higher on-state current, and no apparent degradation of device performance at low temperatures. The mobility of the monolayer WSe2 devices can be enhanced by three to four times, and for single-layered MoS2 devices with the commonly used SiO2 as the back-gate, the mobility increases by 20 times, reaching . The efficient cleaning effect of laser annealing is also supported by the reduction of channel and contact resistance revealed by a transmission line experiment. Further, an enhanced photocurrent, by a factor of ten, has been obtained in the laser annealed device. These findings pave the way for high-performance monolayer TMDC-based electronic and optoelectronic devices with a clean surface and intrinsic properties.

Effect of Ag layer thickness and scan line spacing during laser annealing of Ag/F-doped SnO2 bilayer composite thin films under ultrasonic vibration assistance

To further improve electrical performance of FTO single-layer films and obtain high-performance transparent electrodes, the effects of silver (Ag) layer thickness and scan line spacing on optical and electrical properties of Ag/F-doped SnO2 (FTO) bilayer composite thin films prepared by radio frequency (RF) magnetron sputtering and ultrasonic-vibration-assisted laser annealing were investigated. The results indicate that as compared to the untreated FTO single-layer film, the Ag/FTO composite film displays a dramatic decrease in sheet resistance with even an improvement in transparency when the Ag layer thickness reaches 5 nm under the combined effect of laser annealing and ultrasonic vibration. Furthermore, the XRD and SEM analyses reveal that only using the moderate scan line spacing during ultrasonic-vibration-assisted laser annealing can contribute to the grain growth of the films. The Ag/FTO film with an Ag layer thickness of 5 nm and a scan line spacing of 20 μm shows a remarkable overall performance with an increased figure of merit of 2.13 × 10−2 Ω−1 comparing to 1.13 × 10−2 Ω−1 for the untreated FTO film. This work confirms the opportunity of combining Ag layer deposition and ultrasonic-vibration-assisted laser annealing in significantly improving both optical and electrical properties of FTO single-layer films, providing a promising alternative to the conventional ITO transparent electrodes.

Chemical bonding states and dopant redistribution of heavily phosphorus-doped epitaxial silicon films: Effects of millisecond laser annealing and doping concentration

We investigated the effect of millisecond (ms) laser annealing and doping concentration on the chemical bonding states and dopant behaviors of P-doped epitaxial Si (Si:P) layers grown on Si (1 0 0) substrates using high-resolution X-ray photoelectron spectroscopy (HR-XPS), secondary-ion mass spectroscopy (SIMS) and Auger electron spectroscopy (AES) measurements. Our XPS results showed that the intensities of P 2p peaks for Si:P films were increased with P concentration and subsequent laser annealing. From the SIMS and AES measurement results, we found that P atoms were slightly accumulated at the near-surface region of the Si:P film by the laser annealing, while macroscopic P concentration being maintained in the whole Si:P films without significant diffusion of P atoms toward the Si (1 0 0) substrate. In addition, we performed ex-situ HF cleaning on the as-grown and laser-annealed Si:P films in order to precisely measure the change in chemical states and dopant distribution at the near-surface region. The intensities of the P 2p peak in the as-grown Si:P films were increased after the HF cleaning due to the removal of native oxide layers from the Si:P films. In contrast, the decrease in P 2p peak intensities was observed in the laser-annealed Si:P films after the HF cleaning, indicating the dopant loss from the near-surface region with native oxide removal.

Effects of Phosphorus Doping and Postgrowth Laser Annealing on the Structural, Electrical, and Chemical Properties of Phosphorus-Doped Silicon Films

Phosphorus has low solubility in silicon, but nonequilibrium incorporation of phosphorus exhibits unusual high strain and low contact resistance for advanced Si-based metal-oxide-semiconductor field-effect transistors. Despite recent technological breakthroughs, the origin of tensile strain and electrical deactivation in P-doped Si films is not yet fully understood. Here, by using a combination of experiments and first-principles calculations, we investigate the effect of nonequilibrium phosphorus incorporation into Si lattices and subsequent annealing on structural, electrical, and bonding properties of P-doped Si films. Quantitative structural analyses reveal that the high tensile strain is generated by the incorporation of P into Si substitutional sites irrespective of the distribution of P atoms. More importantly, we found that advanced postgrowth annealing lead to significantly enhanced electrical properties while keeping the same physical states without loss of induced strain. To explore the reason ...

Ultra-Short Pulsed Laser Annealing Effects on MoS2 Transistors with Asymmetric and Symmetric Contacts

The ultra-short pulsed laser annealing process enhances the performance of MoS2 thin film transistors (TFTs) without thermal damage on plastic substrates. However, there has been insufficient investigation into how much improvement can be brought about by the laser process. In this paper, we observed how the parameters of TFTs, i.e., mobility, subthreshold swing, Ion/Ioff ratio, and Vth, changed as the TFTs’ contacts were (1) not annealed, (2) annealed on one side, or (3) annealed on both sides. The results showed that the linear effective mobility (μeff_lin) increased from 13.14 [cm2/Vs] (not annealed) to 18.84 (one side annealed) to 24.91 (both sides annealed). Also, Ion/Ioff ratio increased from 2.27 × 10 5 (not annealed) to 3.14 × 10 5 (one side annealed) to 4.81 × 10 5 (both sides annealed), with Vth shifting to negative direction. Analyzing the main reason for the improvement through the Y function method (YFM), we found that both the contact resistance (Rc) and the channel interface resistance (Rch) improves after the pulsed laser annealings under different conditions. Moreover, the Rc enhances more dramatically than the Rch does. In conclusion, our picosecond laser annealing improves the performance of TFTs (especially, the Rc) in direct proportion to the number of annealings applied. The results will contribute to the investigation about correlations between the laser annealing process and the performance of devices.

Laser annealing effects on Ga dopants for ZnO thin films for transparent conducting oxide applications

Ga-doped ZnO (GZO) thin films were prepared for transparent conducting oxide (TCO) applications. For the first time, Ga was successfully employed as an n-type dopant in ZnO materials. For the ionization process of the Ga dopant, an optical annealing process with a high energy was employed. The optimized contents of Ga dopants were tested and analyzed for the TCO applications. Additionally, different types of optical annealing processes were employed and tested for device applications. Before the optical annealing process, furnace annealing was performed as a basic process, and then rapid thermal annealing (RTA) or CO2 laser annealing processes were performed alternately or sequentially. In our experiment, we found that the sequence of the optical annealing process was important for the effectiveness of the annealing owing to the differences in the penetration depth of the wave and the applied energy density. We confirmed that a specific sequential combination of the RTA process and the CO2 laser annealing process can yield high-quality transparent conducing oxide thin films. GZO thin films post annealed using a sequential RTA and CO2 laser annealing methods exhibited the lowest conductance and transmittance values. Also, by introduction of Ga dopant, thin film can obtain high thermal and chemical stability due to its low reactivity and strong resistance to oxidation.

Effects of Pulsed Nd:YAG Laser on Pt/Ag Thin Film Metal Contacts

This study focused on the effect of laser annealing on Pt/Ag metal contacts deposited on Silicon, (Si) substrates. DC sputtering was used to deposit the metal thin films on the Si. The samples were treated by annealing using pulsed Nd:YAG laser. Then, the samples were characterized based on its morphological, optical, structural and electrical properties. From surface morphological, it is clearly shown that the surface roughness of the laser annealed sample is smoother than the as-deposited sample. The calculated energy band gap was obtained as 1.38 eV. For electrical properties, the resistivity for laser anneal was lower compared to as-deposited sample, which are 5.10 × 10-4 ohm-cm and 1.37 × 10-3 ohm-cm respectively. The conductivity increases when the resistivity decreases.

Effect of laser annealing on thermally evaporated CdTe thin films for photovoltaic absorber application

CdTe thin films were deposited on soda lime glass substrates (SLG) by thermal evaporation technique under high vacuum condition. As-deposited CdTe thin films were subjected to post deposition laser annealing treatment at three laser output energies of 50, 60, and 70 J/pulse. Laser annealing was employed using the laser beam with combined wavelengths of 1064 nm and 532 nm, where the laser energy was varied and the oscillator frequency was kept fixed at 10 Hz. XRD was employed to find the structural properties of the as-deposited and laser annealed CdTe thin films. Topography and surface morphology of the CdTe thin films were investigated using AFM and FESEM, respectively. Chemical composition and stoichiometry of the films were analysed by EDX integrated with FESEM. Electrical properties of the CdTe films were measured using Hall Effect measurement system and the optical properties of the as-deposited and laser annealed CdTe films were studied by UV–Vis. XRD analysis showed that as-deposited and laser annealed CdTe thin films had a mixed phase of cubic and hexagonal structures with the preferential crystal orientation of C (1 1 1) at approximately 2θ = 23.80°. CdTe thin films laser annealed at 60 J/pulse had better crystalline property having minimum internal strain with lower surface roughness and larger grain size resulting in optimized coalescence. EDX, Hall Effect, and UV–Vis results for the film laser annealed at 60 J/pulse depicted good compositional stoichiometry, better electrical properties and optimum optical properties showing the prospects as a potential absorber for CdTe thin film solar cells.

Effect of laser annealing on ZnO nanorods grown by chemical bath deposition on flexible substrate

Integration of nanostructures of semiconducting materials such as zinc oxide with flexible substrates represent a great opportunity to obtain unique sensing platform especially for the biomedical market. However, the attractive optical and electrical properties of ZnO are usually obtained by growing or annealing nanostructured films at relative high temperatures (>400 °C), which are not suitable to substrates made of polymeric materials.We demonstrate in this work that high quality ZnO nanostructures can be processed at relative low temperature (<100 °C) by combining low temperature deposition process and XeCl excimer laser (wavelength 308 nm), used to locally anneal and recrystallize ZnO without affecting the underlying polymeric substrate. We obtain unique post-annealed ZnO nanostructures, grown and processed both on rigid and flexible substrates, that show comparable optical and structural properties of ZnO films that are processed at high temperatures. We discuss the effect of the laser energy density on the nanostructure by analyzing the recrystallized ZnO films through photoluminescence and scanning electron microscopy.